[Vwdiesel] 01 Golf TDi TURBO issues

[Rolf Pechukas]

hi gang
continuing saga of my Golf's poor running issues (after an alternator replacement left the post-turbo pre-intake pipe disconnected for 30+ miles):

I am in 'limp' mode
current error codes - OBD2: P1556 (VW: 17956)
turbo not boosting

waste gate actuator was frozen/rusted, replaced a couple weeks ago
this did NOT fix the issue - promptly re-entered limp mode
(however, turbo DID seem to boost temporarily - first few miles, before limp mode)

we DO have a known bad EGR valve - shop tested, does NOT hold vacuum
EGR code thrown recently (P401 or 402, manager not sure which, but INSUFFICIENT flow)
that code is currently NOT showing up in the scan, apparently b/c limp mode disables testing further downline

beyond that, shop is guessing plugged intake, possible N75 valve problem, MAF valve, or something else...
shop was NOT able to actuate N75 through VAG-COM, they weren't sure why
possible communication problem with their V-C system (?)

again, bear in mind pre-intake hard pipe WAS disconnected for 30+ miles of VERY poor running, barely drivable (and driven 'hard' by the alternator shop to try to 'reset' the computer, also driven several miles bumpy dirt roads by me, all with intake disconnected)

is there anything you all think might have come in through the intake to disable the turbo during that time, or put me in limp mode?
road dust into the intake or head? turbo spewing lube freely froze it up? etc

any other line of inquiry I might follow? any suggestions for shop to check? what order to proceed?

thoughts? thanks,

Rolf in MA