want to know what will perform best in a set up of 400 to 450 hp single 7, already own a greddy ti exhaust tha is a little bigger than 3" but dont know if a bigger pipe will give me best result,but i also been told that i will have more lag etc.
let me know what you guys think

 

More lag? I don't understand that. Correct me if I'm wrong, but wouldn't the more free flowing the exhaust is, the faster the turbo is able to spool?

 

Greddy TR exhuast is 3.75in vband and comes with a mid pipe thats 3.75in vband to a 3in flange. Rx7.com has them, I got mine with the greddy t88 kit so everything is 3.75in with vband.. Its the currect exhuast Ari uses on his race car.

 

https://www.rx7club.com/spec-tuning-154/how-size-matters-478915/

Scroll through the second post till you find where it talks about backpressure.

-Alex