i have an 04 evo mods:

afc NEO, full turbo back, FMIC + piping, BOV, intake, manifold, 660cc injecors, 255fp, and a dual stage boost controller supposed to be pushing 18 low and 23 hi but it pushed 20 low and about 23-25 on high

the problem is that im not sure if its the tune put on the neo or what but around 5000rpm the car like stutters/bucks/holds back/looses power/misfires whatever you wanna call it. i have no clue wjat is wrong with it...ive tried foolin around with my neo, by giving it more gas from like 3000-6500, didnt do anything...the neo reads 10 flat fully opened which is rich...i dont know what to do oh and on top of that i just replaced the spark plus gapped at .026

PLEASE SOMEONE HELP ME OUT...ADVICE WHAT COULD BE WRONG IF THE SAME THING IS OR HAPPENED TO YOU PLEASE HELP ME...

 

is the car tuned? or did you just put the AFC neo on it?

you could be hitting boost cut, or you could be knocking really bad. both of those will feel like a sudden lose of power. the boost cut will feel more like your engine blowing up though.

also, you could be running so rich that it is drowning out the spark. unless you have a wideband on the car, your just guessing at AFR. typically if you are richer then 10:1, thats when you will feel it killing the power, misfiring etc.

 

Yeah, the stock boost limit table tapers down pretty bad up top and that is likely the issue. I do have a question though ... can you not turn down your boost controller to the appropriate levels?

 

660cc injectors are overkill for your mods and undoubtedly making your AFR very rich. I would ditch the S-AFC and get the ECU tuned.