I am looking at buying a 91 formula 350. For some reason the guy tooks the dual cats off and just has a straight ipe to the manifold. I know that the duals cats added horsepower over the older L98's. Did his decision to do this make the car slower or faster????

Cats can only lower HP they are an emmissions control device, it will make the car faster but emmisions will fail if it is checked.

Thanks. I was just curious because I heard once that there is an 0-2 sensor on the cats and that sends a message to the engine about air flow?? Forgive my ignorance I am not too inclined with exhaust systems.

If you have emissions, you better get them on. As far as making your car faster, I doubt you would really notice the difference. Any horsepower would be minimal at best.

Matt

Correct me if I'm wrong, but weren't the O2s on those cars before the cats in the Y-pipe.

Yeah they wouldn't be in the cat itself.. if so.. that would be one expensive cat!

Yeah I'd put them back on if you have emissions testing (well, you may not have a choice there.)

There are O2 sensors in front and after the Cat
To do away with the kitty a sim is needed to simulate the proper signal from the after cat O2 sensor
Removal of the cat wont hurt the car - only emissions like Clayton says

not to get too far off topic here but i think you're correct clayton - i have a '93 and it has an O2 sensor on the Y-pipe and no O2 sensor after the cat and my understanding is that they didn't start putting O2 sensors after the cat until after '95.

Formyla: i think your cars (save for the '79 ta) all have O2 sensors both before and after the cat. could that be why you're suggesting that 4Mula's car does too? i'm sure i could be wrong about all of this but just thought i'd throw my two cents in.

there is no o2 after the cat before 92 at least

sounds reasonable to me Frank
my 00 and 02 have 4, 2 before and 2 after
my kids 96 has 3, 2 in front and one after cat (V6)
my 79 had none when I got it