Right now I have 3inch exhaust from the cat back. THey are putting a 3inch cat and the tubes that run from the engine to the cat will be 3 inches also.
will this be just like headers in performance?
Also, What kind of Horsepower and torque should this give me? It's all magnaflow exhaust.
And I was thinking of putting an aluminum edelbrock intake on. Good idea or no? what kind of hp and torque could i get from that?
One last question, I have 3.73 with posi, when i install the cat and the intake, what kind of performance gains will I notice in 0-60 performance? Sorry for all the questions but I haven't been able to get answers anywhere else.

The exshaust system will help but headers would help even more. A three inch y-pipe isn't nessasary but probably won't hurt either. A new intake is a must and the gears will help alot. As far as gains go could be substantial but unless you do some tuning you might not get as much as you expect. Add a cam and some good prom burning( tune by burning your own proms) you could see a low 15 to high 14 sec. 1/4mi. Add a good set of heads and your well on your way to the low 14's. Hope things go well with the mods you have now and the ones in the near future.

Also welcome to the tbi board.

Steve