Would a slipping belt cause an overboost (high manifold pressure) condition?
I figured if I am going from say WOT 15psi, slip down to 5 (or less), and spike back to 15~16Psi if that rapid change in pressure could cause an intermittent overboost condition? car has a 17%
Also what type of sensor is triggering the code (pressure, hall effect, etc)

 

That was one of the problems we had that was corrected by changing the MAP sensors and wiring harness. if you are getting misfires too, you may want to check into that.

 

You have verified that you are getting an overboost condition (more that 18 psi or so) with a gauge ? If you are infact boosting that high with only a 17% you may want to check for an exhuast restriction.

 

I used to overboost with a 17% pulley all the time, then I added OBX headers, and I never overboosted again. You don't really need a gauge to tell whether or not you're overboosting, as the Traction Control Light comes on and can't be switched off (thus the TC doesn't work)

 

The T-MAP sensor in the MCS is a 2.5 bar sensor, which is linear up to 22.05 PSIg. The ECU is highly sensitive to the MAP sensor clipping and will immediately post a CEL along with the corresponding P0108 code. A slipping blower belt will not cause this situation, and if any supercharger setup is, there is a restriction worse than stock present. A single-turbo conversion upon crossing the boost threshold with a loosely damped boost controller will easily cause this, however!

 

What should be the boost with 17% pulley?