got a 90 gtu, and i plan on doin a full exhaust, but im curious will it lose low end from having less backpressure and how much can i expext to gain from a full exhaust eliminating precats and using high flow cat. im new to peformance with a rotary i was a honda guy for a while, any info please!!

 

With your 90 GTU, you are free to run any kind of exhaust you wish as long as you keep the airpump. This means a good header, high flow cat, and whatever cat-back you will enjoy.

Only S4s rely on exhaust pressure to operate the aux ports, you S5 uses the air pump. So the car will make the most power when all exhaust restriction (backpressure) is removed.

 

yea i was looking into doing the rb header high flow cat and then cat back. what kinda power gains can i expect?

 

About 15HP.

 

wow that much? will i be better off geting the straight pipe with no cat?

 

Slight power difference between straight pipe, presilencers and high flow cats. Whether anyone has dyno'd all 3 on the same car is doubtful, but it's not going to be huge. The biggest difference will be noise. A header + straight pipe is deafening, a cat will do the most noise control, and a presilencer will be the middle ground.