My 2007 mcs has no boost after putting a single mass clutch in. I also put in the GFB diverted valve, no other mods. My Scangauge 2 shows boost range from -11 to 0.1 at wot. HP gauge shows around 112 max. I can hear the GFB valve whistle whe I let off the throttle but definitely no boost. I have checked all clamps including thos on the intercooler, turbo vacuum pump, noise maker, etc and no joy. There is only an occasional p115d error code on the scangauge with no other errors. Stuck waste gate maybe?

 

check the plugs going to the BOV and MAF. also check the thin vac hoses.

 

Any update?

 

Well I've checked the vacuum lines going to the wastegate. A manual vacuum pulled on it shows the rod moves about 1/2" at 10" of hg. With a "T" inserted into the vacuum line, engine on, shows around a 27" vacuum with the waste gate fully closed as expected. Blipping the throttle shows the vacuum drop to 10" so under a real load I would expect it to open when the vacuum drops even lower, again as I would expect. So there is only 2 places left that might explain the loss of boost. The noise maker or insufficient back pressure from the gasket between the down pipe and the flex joint/tailpipe. Or perhaps the ecm is telling the wastegate to open due to some other issue. I'm still getting the P115d error but not as often after cleaning the maf sensor. Also after the cleaning I did see a momentary 4psi boost which is the most I've seen. I'll be removing the noise maker today following bimmerdudes video. Also looking into adding an occ and the dual boost mod with plugs. I'm stumped so far but there must be a reason for the little to no boost. I will keep looking. And thank you to the responders of my plea for help.