Well today was the happy day where i took off the crappy FLowmaster, and put on the new SLP Loudmouth! I have finished installing it, but after i drove it around a little while, i noticed there is quite a significant amout of exhaust "pop" when letting off the accelerator, it seems like there is more than there was with the flowmasters. Also, at a stoplight, the car was vibrating pretty decently, making my hand on the shifter tickle a bit. It was definately more than normal. Anybody know what these symtoms could be from? I checked under the car when i parked at my school, and i noticed there was some exhaust puffs coming from one of the joints by the LM resonator...i think its a leak, but i'm not sure if this could be the cause of the vibration and the popping? (oh and the vibration only happened one time so far, its not every time i stop). THanks guy! I'm gonna try tightining it down later tonight and see if that does the trick!

I'm not sure what might be causing your "popping" but I know when I first put the Magnaflow catback on my 4th gen cars that they "popped" if I either revved up or was going highway speeds and let off the accelerator quickly. I done a post about it and was told by members here that it has to do with "unburned gas vapors" burning off. If you do a search you can probably find the threads about that.

The "popping" lasted on both of them for about 6-8 months, slowly decreasing over time. Now it only does it on my 97 if I have the car in park and rev and left off the gas pedal very quickly (stock headers and Y-pipe). My 99 doesn't do it at all, probably cause I've got LTs and an ORY on it but I'm not sure.

As for the vibration, I'd check to make sure that everything you removed is tight again and that nothing is hitting anything it shouldn't.

something else to check regarding the vibration...when I first put my catback on I didn't get the I pipe all the way into the pipe that goes over the axle and the driveshaft would hit it occasionally.

My LM still pops(installed for 3 years) sometimes like Sue's Magnaflow at idle with throttle blips, and if I've got the motor wound tight in any gear and let off the gas, it doesn't always pop but it doesn't suprise me if it does either. My y-pipe to mid-pipe connection slightly leask too, but not enough to see puffs of smoke, just enough to see some condensation drips and light soot on the pipe. I don't have any extra vibrations that I think are anything more than what the polyurethane tranny mount causes. Since I installed both LM and mount at same time, can't tell for sure. Before the LM, I did get a vibe/rattle from a loose heat shield against the y-pipe that only occured during acceleration. I suggest checking the length of the exhaust for loose connections, parts, or close tolerances.

As far as tightening clamps, be sure to take it relatively easy on the u-bolt style ones, they can crimp your pipes.

Thing sounds mean thought, right?!?

I checked under the car yesterday to try to figure out what the vibrating was coming from...and i THINK i know what it is. The pipe which arcs over the rear axle is VERY close to the panhard bar, and i am almost positive that when i am driving, the pipes are vibrating cause of the exhuast pulses, causing it to hit the panhard bar. I am going to do some fiddling around with the exhuast tomorrow or sunday to try to reposition it to give it some more space. However, the ONLY thing that throws me off is the fact that, when i put the car in N at a light, the vibration stops. It ONLY occurs when the car is in drive....any ideas?

look a little further towards the front of the car. the metal crossmember that goes across the driveshaft tunnel is where mine was vibrating there's less than a 1/4 inch clearance on mine was less than that..hope that helps
also in my opinion the popping adds character

yes - i like the pop!

Clearence decreases on one side when in gear the motor torque pulls it up I'd have to look at one running to see which way it pulls. Pop the hood - rev the engine - see it twist? Does the exhaust hit anything when you do this? That is where you need to lower the pipe and retighten.

Hey sorry i havent been on in a while...my internet has been down for a few weeks. Yeah i still havent gotten to fixing the vibrating, but i plan on doing it tomorrow, i've just been so busy lately. Thanks for all the tips on where to check, i will be sure to check all the way down the driveshaft just to make sure. I took a quick look at it when it first started happening and there seemed to be plenty of room along the driveshaft, however i havent checked it while the car was in gear. I noticed that the popping has died down quite a bit, but yeah it sounds really sweet now. Especially when letting off the gas the popping noise sounds veerrryy nice haha. Makes it sound like more muscle :-D

okay well today i FINALLY went under my car and messed around trying to take care of the vibration. I went ahead and loosened all the pipes and rearranged them. I cleared the panhard bar and the car STILL VIBRATES! So after driving around and it started doing it again, i pulled over in a pool parking lot by my house and put the car in gear (it only does it while in gear at a stop) and put the E-Brake on. Then i got out and looked under the car. I checked the clearance over the panhard bar and it was fine. Thats when i started looking at all the piping and i noticed that the y-pipe on the driver's side (the section between the cat converter and the section where the y-pipe comes together) is vibrating more than it seems it should be. So i just waited for the car to cool down and looked under it. The bolts seem to be all snug, however i havent jacked it up so i dont know if it could be coming from where the manifold attaches to the cat. I just dont know what could be causing it to vibrate. I checked under the hood where the manifolds connect to the block and it seems fine. The engine runs smooth too and isnt rough so i dont know what could be causing this? So now i am totally confused. Help would greatly be appreciated!

...anybody?

I don't know how much this will help you or not, but on my 99 after I put the LTs and ORY when the car is in drive and I'm stopped for a light, stop sign, etc. I have what might be called a "vibration" by some but to me it's more of a couple of rattling sounds. I know what both of them are though. 1 is from the heat shield on the drivers side by where my feet go, the other is where the LT/ORY hits slightly against the brace that runs under the tranny. When I put the car in neutral both sounds stop. The sounds are caused by the way the engine "vibrates" (for lack of a better word) which causes both of them to move. There's not much I can do to stop either one short of removing the heat shield and lowering that brace so I've just learned to live with them.

As Far as the POPPING goes, when the motor is reving at significant RPM levels and you quickly take your foot off the gas or put it in neutral between gears, there is a lack of continuous back pressure leaving the motor. Its like a bubble of pressure with nothing in front or behind as it comes down the pipe, just like a bullet leaving a gun.

Since most of these performance exhausts dont have baffels in the mufflers or dont have mufflers at all there is nothing to stop the back pressure and it makes a popping noise.

You can try easing off the gas when you shift instead of taking your foot all the way off or "power shifting" keeping the gas halfway down while pressing the clutch and shifting gears.

My '01 formula does the same thing but by altering my driving style I havent heard that noise in over a year