Im having the same problem on my 05 MR... No cels.. Stock evo9 dv valve.. ETS intake.. BPR8ES plugs.. is tuned by Sean Ivey.. Ran awesome then one day just would boost to 15lbs and thats it and starts to break up real bad.. I made a boost leak tester yesterday Im gonna do a leak test this sat.. Hopefully its just a boost leak but Im thinkin its somethin else..

 

Maybe the clutch is starting to slip.

 

Do a proper boost leak test, also check your t/b seals. It's grossly underestimated what a boost leak can fix. Cam sensor too

Boost leak
T/b Seals
Cam Sensor
Wga

Id do that order for starters

 

for me, it was my spark plugs, put some BPR7ES in and boom, no more hesistating

 

How do you check the cam sensor and the wga?

 

What do you mean? You dont know were theyre located, or you dont know what your looking for?

 

Cam Sensor would probably need to be resistance tested, or voltage tested depending on its signal.

WGA , you need a hand pressure pump, apply 17in/hg of pressure and the rod should move. we just put a air sprayer tip on our air compressor and just open the valve a tiny bit to leak out 17psi and make sure it moves. kinda the easy cheaper way then a hand pressure/vac pump.

 

Thanks man.... Ill give it a shot...

 

Do the cheap things first. Check plugs and gap mine at .022 and do a professional boost leak test. A couple of months ago my 2003 VIII evo had the same problem was boost leak couldn't find it/see it or hear it myself. Runs great now once I got it fixed.

 

this same thing happens to me it really annoying. i dont have a cat so its not that im gonna change plugs and ill let you guys know

 

Update on my car... Changed the plugs today and fixed my problem no more hitting 15lbs and chugging now hitting and staying at my tuned 26lbs.....Thanks for the help guys...

 

I figured out my issue, in case anyone has simillar problems, felt like either a boost leak or bad plugs. it turned out that I pulled the fuel pump, and the gromet that sits on the stem on tp of the pump like a cap had slid down and excess fuel was just being sprayed out the sidees i guess and back into the tank. That OEM gromet probably got worn from age and me pulling it out once before just did it in. the replacement cost i think 2.00 on stm's site. Hopefully this gives a little help to anyone feeling the same thing!

Thanks again for all the suggestions!