overboosting, new mbc

[talonite]

ok so just today my car overboosted like CRRAAZZZYY it was set for about 14psi on a cheapy ebay MBC, but yet it built boost to around 24 to 28psi. so i figured that was the problem. bought a new grimmspeed MBC from MAP thinking it was gonna be a clear solution. but it is still doing it. im running an evoIII turbo with the stock internal gate on it. any ideas on where to start? I mean i triple checked and everything is hooked up correctly, and I'm just kinda stumped at the moment.