You probably wouldnt want to. You would lose a lot of backpressure and it would be MUCH louder than the usual position. Most place it before the bend over the axle, there is an indention in the floorpan there that fits the cutout nicely. Plus the stock y-pipe on a single cat car is not 3" and the y pipe comes into 1 piece at the cat.

 

I ran mined on the dyno, one with and one without, and i only saw 3hp. but my cat was already gutted, so if your is not then you might see more. Dont expect much hp, just sound.

 

there is no room to put it before the cat....and my car feels faster w/ the cut out closed....maybe it is just me, but I would swear I lose power w/ it open.

 

i ran 13.73 with it open, 13.74 with it closed. same launch technique, same lane, same 60 ft. back to back.

and i have what a lot of people call a "restrictive muffler" the flowmaster.....must not be too restrictive. i also have long tubes, and no cats.

 

i'm thinking my completely stock exhaust will benifit, definitely with hp, hopefully/probably with torque as well. I have alot of backpressure, and i figure the cats will retain enough that it'll keep my torque up... I dunno, we'll see, once i get it on i'll do some back to back running.