Well, if the compression is good, then I'm not sure the gasket is bad. I was thinking that if the compression is low, maybe they used too thick of a head gasket. Turbos generally have a thicker head gasket than N/A's, but maybe they used one that's too thick??

You're running 15psi on the stock turbo according to a calibrated boost gauge, eh? (I'm assuming you removed the overboost fuel shutoff switch).
Do you have any type of fuel system mods? Like a RRFPR? Are you running too lean? Ignition might be retarding because of running too lean and it's effects.

How's the temp outside? Was it really humid when you ran at the track? Mine's extremely tempermental when the humidity gets up there and the temp is high. I've hit 16.12 @ 87 (I was beaten by a CIVIC!!) in the 1/4 in mid july @ 97 degrees. Try running it in the winter or fall. Turbos like cool air.

Also, if you're on your stock turbo...I'm guessing a T25... they're way out of their efficiency curve at 15psi. As antithetical as this might sound, try lowering the boost to 12psi and see what happens.

One more thing: check to see if the cat. is clogged (yes, I know this would cause rich running and black smoke and you said there was no smoke), check intake plumbing, clean the throttle body, check the injectors blah blah blah.

Hope this helps, sorry for the excessive amount of info.

Ryan