Originally Posted by CHUNKYS RS

i have a sierra 4x4 on a j the problem iam having is trying to set the boost, i tried driving up the road in 3rd gaer at 3000rpm and foot on the brake and set it to 16psi as stated in the paperwork with my msd chip.
i thought that was it but under normal driving as the revs pass 3000 the boost starts to go passed 16 and by the time iam at 4500 the boost is up to nearly 20psi
so i thought it might be amal valve or actuator these have both been changed and i have checked the wastegate is not stuck
if i sef the boost to 16 at 4500rpm then when i floor it at say 2500 i only get 11-12psi ,i have also put the actuator pipe straight to the turbo but no different
it has a -31 collins actuator stage 1 chip and scorpion exhaust but other than that is standard
any ideas!!!!!!