Erratic/spiking overboost

[Commando14]

Ok, so having a new issue with my RB. Essentially the boost is building erractically, and its spiking up ~30+lbs. The car doesnt feel like its making power and it just overall doesnt feel right. The turbo is a pretty much brand new GT3071r, internally gated, with the newstyle gt flange. The wastegate has an 18lb spring. I checked and reran the vaccum line from the manifold to the wastegate. As well as the vaccum line to the MAP sensor. Its run on a Haltech 2000 w/ 3bar GM map sensor.

edit: my bad, its internally gated, not external.

[Darius]

Not to ask a dumb question right off the bat, but are you sure the map sensor setup table is correct for a 3 bar sensor? It should only read up to about 29 psi (-14.5 psi to +29 psi = 3 bar).

Here is an even dumber question, you have a boost control solenoid valve, right?

[Commando14]

It was tuned pre-headgasket and now this, troubles, and I havent touched the ecu or maps or anything. It was tuned at 18lbs, (it rose a little to 20lbs at high rpm, like, 6k+ but was stable). A buddy works for grimmspeed, so I grabbed a MBC from him to just try that quick, and it didnt change a thing.