help identifying boost leak
 

hello,
my S4 13BT won't boost past 4 or 5 psi, when it was boosting up to 15psi until recently. I am assuming that there is a boost leak in there somewhere, but even tho i have looked over the engine bay, i can find no obvious leak!

is there any common list of failure points that i can scrutinize?
any troubleshooting FAQ? i searched the previous posts, and didn't find much other than FD owners lamenting their boost troubles.

Is is possible that the engine has let go, and not enough exhaust gases are being created to properly spool the exhaust wheel (i always think the worst)?

I can see some oil on the turbo, so there is a slight leak somewhere there, and on the exhaust side, there is a little white streaking, which i can only deduce is a small exhaust gas leak, but both of these have been there from the time the turbo was put on, altho annoying, they don't seem to be causing any probs. the FMIC & piping is all tight, vacuum lines all seem OK (where i can see them)

i *did* put a boost guage on a few weeks back, but it everything was working fine with it....it still reports the same boost reading as the Microtech Handset...


Any thoughts? i am fucking stumped.
Is there any way to measure the pressure immediately after the turbo, so i can work out where the pressure drop is occuring?
Should i be able to hear the leak at all?

Thanks 4 any advice,
Perry Gehenna