I have an Evo 9 mivec 2.3 stroker.
-Link ecu
-pte 6266 .82ar
-GSC R2 cams
-GSC spring and retainer
-GSC zero tick lifters
-English Racing underdriven oil pump gear(retards 2deg)
-oem exhaust cam gear
-fic 1650, Walbro 525
-spoolinup cop kit
-denso ikh24


When tuning the car does great on spring pressure(16psi). Making around 450whp and 350 torque. The problem is when we add any boost let’s say 5 psi. We get a spike in power and then the power band falls off and makes less power then it did on spring pressure. No boost leaks, boost is holding consistently.

Me and my tuner have looked through everything as it seems like there’s a restriction but there isn’t. My exhaust goes out the hood so should be no problem there. The only thing that I’m thinking is something with timing as the oil pump gear retards timing on both exhaust and intake cam 2 degree and my exhaust cam is not adjustable.

if anyone has any advice it will be much appreciated because I’m stuck on what to do at this point.

 

I have the ER underdrive pulley installed on my 4G64 2.4L build and didn't face too many problems with timing it. I do have adjustable cam gears installed but that is mainly to bring timing in line with the added 6mm deck height.
I believe a WOT log for both spring pressure and added boost would help with troubleshooting.