If there is a decent leak in the intake to throttle body and you're running MAF, then you're idle would be affected.

If it's a small leak that is only effective during boost (hence boost leak), then you need to pull each hose off and inspect for small cracks. What kind of clamps are on the intercooler piping? I've blown out IC hoses on a couple of FC's. It usually makes a big pop noise and you lose power as a result (no boost).

I'd go over it again as well as the clamps (look for out of round clamps, etc) since it's a whole lot cheaper than a turbocharger. It's odd that it would "let go" at 10psi and yet not have any play and spin freely.

When I blew the 62-1 in my FD, it still made boost even though it had plenty of shaft play. However, I didn't want chips of metal going into the intake of the engine so I replaced the turbo.

You'll produce boost if it has play or if the fins are bent (not too much). If the turbo is "locked up" then you may have a big problem.

You can also try putting the stock IC on it and see if it helps (maybe a new clamp/piping is causing the leak).

J

 

One more thing came into mind...
I was helping a guy with an FC the other weekend and I remember that he had signs of gasket leaks around the UIM and LIM.

Another place where boost leak can occur, but the idle affects may vary.

J

 

if push comes to shove do what us guys in the aviation business do. Pressurize the system. On aircrafts with turbosuperchargers we pressurize the system with a vacuum or compressor and soap/water spary the pipes. just a suggestion.

 

You DON'T have any sort of intake leak.
That I gaurantee.
If you did, the car wouldn't idle, would run badly, and if it was tiny enough to not make the car run horribly, it wouldn't affect boost one bit.
It could be a split hose, that would stay closed untill boost hit- opening wide open, but you would still probably get a bit of boost- plus you'd hear it like crazy.


It's your turbo- it has to be. You heard a loud pop... could have been a backfire that knocked half of the turbine apart? Who knows...
I bet any money you will find your problem if you take off the DP and look at the turbine wheel....
Something could have come loose, or broke apart (the twin scroll actuator maybe...) and jammed in the wheel.