A compression test is done with the throttle wide open, ignition and if possible fuel off and the starter turning it over. 90psi sounds about half or what you'd get if the throttle was closed. It probably says in the tech section how to do it correctly.

yea turbo seals gone by the sounds of it, blue smoke is usually the indicator. it wont affect idle, if your engine has overheated it could of overheated the turbo bearing and affected your seals i guess just depends how you were driving when it overheated

just had a thought, that if my engine overheated enough would the water line and oil line get that hot that the oil gets that thin n stuff the seal, and same thing for the water?

it dose not blow anything at idle just under boost and the more boost the worse and intesne it gets.

idle is pretty constant never goes up or down just above 500rpm, could a stuffed turbo affect the compression levels, i have a feeling my timing is out which is why it idles low,

adjusting the idles screw would be my last resort,i will check today for oil in the intake

I agree with John, or maybe it is a ball bearing turbo? if so do you have the restrictor in the oil feed?

Turbo seal is gone pretty sure needs a rebuild

no exhaust shouldnt affect how it runs at all....it has a turbo it needs no exhaust after that

is the idle constantly low? or doesnt it rev up and down when idling?
mine used to have a crappy idle and then die if you got off the throttle quickly and i found that the BOV itself was leaking so the engine was getting lots of unmetered air. as soon as you put your hand over the outlet of the BOV it would idle fine

yeah i can rev it up n hear the turbo making a noise whe i shut the throttle but just dies down in reves n shuts off..

i would pull the front hose off the turbo and check for oil there... if there is it's a problem with the breathing

have you been revving it up and getting it on to boost?

idle is simply set by a screw on the throttle body, the one the rotating throttle piece (cable is attached to) hits when it return to the normal position, if you want to change idle then just screw it up or down to achieve what you want

if the smoke is coming out the dump pipe then its either leaking seal in turbo, leak in cylinders in motor or if like me recently there is oil coming from the motor into the inlet in front of the turbo because of dodgey PCV valve/blocked air filter/no catch can

BOV could not affect any of this, no exhaust is certainly gonna make it run poorly and affect idle