I was thinking about exhaust mods, but I really want to keep my car as a "sleeper," I dont want an exhaust that makes alot of noise. I was wondering if you could get a performance gain from maybe adding another muffler (simular to the stock one) and making a joint in the pipe somewhere. Is this feasible, or am I way off of the target? Any replies would be great.

I Would say get a dule muffler so you will get better flowWhen i say dule muffler i mean an muffler with 2 outlets. ALso get an oversized gigh flow CAT

I do not know if you have a U-bend in your exhaust for the seccond O2 sensor but if you do you should replace that with a straight pipe