How big is the diameter of your boost line from turbo-housing --> manual boost controler --> wastegate? Mine is about 5-6 mm and I think it is too big to adjust the boost accurate. I turn the **** on the manual boost controler (from fully closed) only 20 degrees and the boost is overshooting.

Would some kind of restrictor in the boost source help?

 

*shouldn't have gotten rid of the AVCR* Cough... 6mm sounds about right. I believe 4mm is the small vacuum lines that run through the intake mani.

 

I still have my AVCR, but I turned it off for boost setting. I try the trick with the restrictor for more accurate adjustment with the mbc.