hi all problem is that my cossie will only boost to 15 psi

car spec
greens,3 bar,-31,chip stage 3 , scorpion,4x4 intercooler,bleed valve ,

i changed the amel valve cus it would only boost to 10 psi now the bad boy only hits 15 psi standered turbo its 2wd

1 acurater i have hits about 19 psi and drops to 15 psi the other hits 15 and stays there car still pulls well

any ideas would be top