Thanks for the information. I have been trying to work things out and find out what is the problem. I do not have a PD engine, it is the mid-level 110 hp engine with variable vane turbo (VNT15?), engine code ALH, which is basically the same as ASV. There are some more details (including vagcom logs) at seatcupra.net if you are interested:
http://www.seatcupra.net/forums/showthread.php?t=280772
I am planning on switching the EGR (N18?) and boost control (N75) solenoids and relogging data to see if that improves the boost control. Edit... just checked and the electrical connections are different, so they can't be swapped directly... which sucks.
The other though I had is a messed up MAP sensor that is reading a higher pressure than actually exists (I guess the opposite of the MAF which tends to read too low airflow when it starts to die). Short of buying a new MAP, I am not sure how to test that.
The turbo has already been cleaned and a cracked oil return pipe from the turbo was just replace a few days ago. That replacement pipe seemed to have make it much harder to get it to go into limp mode, but it still appears to be overboosting based on the vagcom logs, so all is not well...
If you have any more insight, definitely share. Once I get this problem fixed, I will be turning down the EGR in Vagcom or putting in a blanking plate. My car my be old enough that I could simply unplug the EGR solenoid and not throw an error code... so maybe I will try that first.
I am getting about 6L/100km right now with a lot of highway driving (about 40 miles/US gallon). I thought I may do a bit better, but maybe the turbo issues are throwing things off.