10+psi boost spike=30+psi

[dragrush]

Im trying to set my boost to 27psi, but it spikes to 30+psi and then drops down to 20psi. Here is my dyno graph with boost reading for exmple (green line is boost)http://www.dsmtuners.com/gallery/showimage.php?i=77801&catid=searchresults&searchid=22849

On this dyno graph I had Greddy profec II EBC and large blue Tial WG spring (14.5psi) It went from 28 psi down to 18
Now I have the large and small blue wastegate spring (23psi) and Hallman Prob MBC and now the boost jumps to about 31psi and drops down to 20.

My MBC boost contoller is turned all the way down, but if I turn it up to get that 20psi boost level higher the higher the boost spikes (too high) I just want it to get to 27 psi and stay there, but cant seem to find the problem. Also the boost shouldnt be falling below the 23 min wasteaget spring rating correct?

....once the boost gets to about 25psi the wastegate starts to open it spikes to 31psi and drops to 20psi and the external wasteagte is open the whole time. Any idea what the problem can be. I took it to a few local performace shops and they say seems like the turbo is going. What you guys think?

Things I checked:
Boost leaks test to 30psi-None
Compression test- 165 on all 4
Leak Down Test- less than 8%
Properly Tuned
Min turbo shaft play
2 different boost controllers (MBC & EBC) both hooked up correctly
Stiffer wastegate spring (min 23 psi)
No exhaust leaks

 

[92dsmtalon]

Any intake leaks, or your Crank Positioning Sensor may be bad too. A buddy of mine had that happen to his 95 TSi and his CPS was going bad, possibly going to crankwalk, but his intake manifold gasket was shredded, when he replaced it, the spike went away.