gotmashed

ive got a huge problem ive got a 93 wrx with a garret TD05 18G with exturenl wastgate and screemer pipe fmic and had her chiped and maped so i can run 18psi but the waste gate opens at 7psi now to startwith i thought it was my boost controler but having tryed fitting a bleed valve to see if this is the case no still only boosts to 7psi theres no leeks does anyone else have a exturnel wastegate ? is there something im missing