Stock evo8 bumper
Gialla
or C West? I like their looks all equally so now im gonna choose based on aerodynamics

 

If your going to get the Gialla or C-West bumper, make sure u get the whole aero system. These "aero systems" (not body kits) are designed to work when you have the whole thing, meaning the front bumper, side skirts, and rear bumper (provided they have sides, and rear bumpers, i'm not sure if the Gialla kit does ). These JDM kits are proven to lower race track times by as much as a couple of seconds, and are designed to provide more downforce. So either one you decide on, consider the fact that these won't work as intended unless u buy the whole system. Good luck on picking. Go here to see what I'm talking about:
http://www.c-westusa.com/labs/fudo1_s2000spec.asp

 

thx, i think the Gialla rear is SUPEr ugly and the C west rear is just ugly, but i'll consider the front/side skirts option as well as canards and maybe a rear diffuser

 

wind tunnel test are crazy. i wish they had video

 

Stock!!!!!!!!!!

 

I cannot answer your question about aerodynamics; however I do remember reading something from a JDM tuner article about the cwest bumper coupled with a larger FMIC provided around 8 degrees (F) drop in the temp of the intake charge. I'll try and find the article.