Seems like lots of people have had similar issues, but nothing matching mine exactly. I just got a 96 Evo IV which came with an HKS mushroom style intake, exhaust, turbo timer and gauge. If someone could help me out, I'd really appreciate it. Thanks in advance

Whenever I apply a lot of throttle (60%-WOT), the car stutters/pulsates and struggles to accelerate which feels like a fuel cut. Low throttle is no problem. This happens regardless of RPMs. Boost also struggles to build past ~0.6 bar. The stuttering doesn't seem to occur in 1st, and only very slightly in 2nd but becomes progressively worse as I go into the higher gears. In 5th it is downright awful. The stuttering also becomes worse as I add more throttle. Once it stutters, I let off, and a few seconds later, the cat overheating light comes on in the dash for about 3 seconds then goes away.

I have changed the plugs and cleaned the MAF, but no difference. Any ideas of what I can check next?

 

mine did the same thing..it was foul plugs..do that if it doesnt helps try a boost leak test!

 

Thanks! I'll try to look into doing a boost leak test. Also, what is the normal amount of vacuum at idle? and while coasting at 0% throttle?

 

my vaccum is at 20 when idling..do u have a wideband?

 

Nope, no wideband. What units is your vacuum expressed as?