What gets the most horsepower for a mod?

I could tell a performance improvement when I replaced the stock muffler with a flow thru muffler.

Is it worth looking at getting rid of the camaro style muffler with one inlet and two outlets? Is it possible to go to a dual exhaust system?

I am looking at ...

I have 77k miles on this car, and have had it since about 30k. Last year I bought a flowthrough muffler and was pleased I could tell there was an improvement in the acceleration from the seat of my pants. :banana:

I just had the sc serpentine belt come off due to a failed idler pulley and noticed ...

I just had the 3" grooved idler pulley collapse and so need to replace it. I just joined the site and found your photo of the belt routing to be very helpful.

I noticed my my full throttle power was gone and then noticed the boost gauge was not going above 0, so I poppped the hood open and found ...