not really sure what it is when your just about to hit full boost it stops reving and make really loud bangs and just holds back the boost gauge will flick between 15-20psi but revs wont increase and logs so no cf's and nothing jumping out as a
problem and no fault codes come up at all.
Hmmm, What does your rev counter do when all this is going on?
I'm thinking at the moment that it could be a couple of things;
Ignition Timing - Check your belt timings, as you rev harder your timing is automatically advanced, if your timing is slightly out, your ECU maybe winding it too far forwards causing firstly, your lack of power and secondly the backfiring effect your getting when the power loss happens.
Basically, backfires are caused by fuel sitting unburned in the cylinder and being cleared out through the exhaust, if your spark is in the wrong place your effectively making a mortar cannon out of your system when this excess fuel is ignited, sounds cool but doesn't do much good for your emission control.
May not be the issue but worth checking on all accounts..
Fuel Supply and Delivery - Get your injectors pressure and flow tested, make sure your not spitting bubbles instead of spraying mist, might also be worth checking your throttle body is clean and aligned correctly.
That should be enough to keep your mind ticking for a little while.