Overboosting to 18psi, Spring Set at 15psi - Why?

[Clinical]

Okay so back in February I had an issue with my manifold->turbo gasket blowing due to a cracked turbine housing.

I got an new housing, put everything together and it worked fine.
Although my wastegate spring is set for 15psi.
I have a Tial 38mm External MVS Wastegate V-Band.

The car is boosting to 18psi now in WOT.
I just figure with the 2-3 weeks the car sat, I messed the vacuum line to the wastegate up somehow.

I just replaced the vacuum line and it's still boosting 18psi.
What else could cause the car to overboost like this?

I'm about to hook up my MBC and turn up the boost to 21-22 but want this fixed before i do.

Thanks for any help.

 

[liquidz28]

is the car at normal op temp when it is overboosting? also have you done any looking for boost/vac leaks?

 

[DSMGUY420]

im actualy having that same problem except i have a internal wastegate on a evo 16g turbo and a electronic boost controller that and mine stays at 10 lbs no matter what i do and then out of nowere its actually hit 22 and i have no clue why

 

[Clinical]

It's always at Op temp when I hit boost. I always allow 30ish minutes of driving before I hit boost at all.

I in fact just did a boost leak test yesterday when replacing my vac line, only place it leaked was the bov a bit. I knew that leaked however, in fact my new BOV should be here either today or monday.

 

[liquidz28]

WG dont open fast enough causing creep, i i dont think thats an issue really, 1 millisecond of 20psi on a 18 psi setup wont do anything bad, well accept maby blow off an ic pipe, but if you keep your shits tight, your good. dont worry about it. the stock t25 has boost creep like a mofo, i think mine would go from 15 to 17 just when i hit max boost while it was to the floor, i watched my gauge and it spiked to 17 right when the pedel hit the floor but go back to 15 just about instantly.
how long does yours spike or is it the same as mine?