this is my friends car, im tryin to help them out. car is an evo 8 with an fp red(older style), intercooler, o2 housing, full exhaust, and gsc stage 2's .

it was tuned for 26 psi on 91 octane about a week ago. recently the car began breaking up badly up top. i checked the plugs and they were gapped at .030 . I brought them down to .025 and it is better, but its still happening. We turned the boost back down to 20 psi and obviously now everything is good. Although i think the plug gap is playing a role in this, the car did run fine for an entire week with no issues which leaves me to believe that something else isnt right.

any advice/suggestions are appreciated.
thanks
-Alex

 

which spark plugs are you running?

ALSO

you MIGHT want to check the EGR valve hoses. i had this SAME issue pretty much. if you reach under the throttle body, the EGR valve is down there. feel around. you MIGHT find the culprit.

 

bring the gap down a little more. maybe to .022 or so. i would even grab some new plugs. also i would log the car to make sure u are not getting knock. the ecu will pull timing causing it to "break up".

 

Gap down to 0.020 and see.

 

are you running proper iridium plugs? if you gap them down you scrape the iridium off the tips and render them "useless" (i.e. no longer iridium)

 

Yeah make sure they arent coppers. my car ran terrible on coppers

 

+1000000

try to get HKS twin power on ur car coz i had this problem on my car but when i got the HKS twin power the problem is gone

 

I would just change the plugs..

 

possibly coil pack issues?

 

how many miles are on the coil packs?