I just bought a DC 4-1 JDM header(remember 2 1/2" collector)...now, do I get the 2 1/4" or 2 1/2" piping done...I'm ready to get the exhaust done, all I have now is a muffler and no resonator w/ factory piping, cat, and manifold. I just went to OBD 1 and I chipped the ecu tonight w/ the XS program, I would think the 2 1/2 would be better. I'll be having a new cat installed also w/ the new exhaust. Tell me what ya'll think and why...please no smartass search bullshit either, I need up-to-date opinions. Thanks.
mods-CTR cams (untuned), AEM CAI, OBD1 ecu, MSD 6AL, Arospeed muffler...I plan to stay N/A, at the most I might by another ZEX setup due to ease of install and the fact that a 65 shot dry is really all the extra I'm looking for, for the $$$.

 

Depends what you want to do later on.

2.5 will be better with high lift cams.

2.25 will be better with a I/H/E setup.

 

if i remember correctly the jdm 4-1 has a 2 1/2 tip right? i think 2 1/2 would be better for you.

 

Would going from the JDM header to 2 1/4 cause unwanted results or no problems. I am considering Skunk2 stg2 and full headwork around Christmas time, I'd rather spend the $$$ and do it right the first time.

 

i would go for the 2 1/2