I have both systems already, but need to install one on the 2000 Formula... Which do you guys think would be the best sounding on an LS1?

From the mods you've got listed I take it that you have headers on the car? If so I'd go with the Borla. Loudmouth is nice but I've heard a few cars with it on that have headers (long tubes ) and they all had alot of rasp. That's not bad, don't get me wrong, if you don't mind the rasp or you don't drive the car very often but to me it would get annoying after a while on long drives or if I drove the car daily.

Yeah, I dont know which to choose! ahhhh!!! Need sound clips I think! haha

Sound clips? Ask and you shall receive.

Here's a link to a site with a whole lot of sound clips on it: LS1 Sounds

wow i haven't been on the forums in a while lol! glad i saw this thread. I have heard both exhausts up close. First things first, i would like to say that BOTH exhausts are excellent choices in my opinion. I have the SLP LM 1 on my car, and to be honest i love it. The price is awesome, the quality is great, and it sounds so so nice. HOWEVER, i have also heard that they do get raspy when longtube's are put on the car.

Now for Borla, a good friend of mine has an 2000 Formula that is modded to death, and he's got the SLP longtubes, no cats, and the Borla with open plates. To be honest, when i first heard it i didn't really like the sound of it. I expeced much more out of it because of the "Borla" name on the exhaust. It is pretty quiet at low RPM's, but as soon as he revved it and when it hit a certain RPM it screamed like an Indy car. I fell in love with that sound. It is a totally different sound than the SLP's Loudmouth. If you like raw V8 loud exhaust, personally i would go with the Loudmouth, but if you like the refined exotic V8 exhaust note, strap on the Borla.

On a side note, if you do decide to go with the SLP loudmouth, but also want to put on Longtubes, you can always switch off the LM resonator and put on the Borla resonator. There are also a few other resonators out there made by different companies. Just check out ls1sounds.com that Sue suggested. I will attach a few links of video's of my car revving with the Loudmouth.

the rev http://youtube.com/watch?v=_75vS7mKIag
driveby http://youtube.com/watch?v=1Lh2J74KnlA&feature=related

With the stock cam the LS1 does sound a bit tame at idle and real good on the throttle.
Once an after market cam is installed the LS1's rumble at idle nicely - with an after market cam the loud mouth gets really uncomfortable

Out of those two, go with the Borla... IMO Corsa is best (no rasp, subdued noise level at cruise).

Great! Thanks for the help!! I will be going with the Borla!

You're more then welcome for the help since that's what we're all here for.

Nice choice! What are you going to do with the other exhaust? Sell it on ebay or something?

I am looking to buy an exhaust...if the slp is for the right price id take it off your hands