euro_2nr: Thanks, I picked up a 710N and will swap it out soon. hopefully that is my probelm. In the meantime I will hook up Vag-Com and log blocks 115 and 032 (boost levels and fuel trim).

 

I have recently purchased a 180bhp tt with a blown turbo.
The problem i have had after replacing turbo cat plugs cool packs all the normal parts is surging.
I have searched everywhere for a answer vac pipes boost pipes all changed to no avail.
Finally I removed some pipes under the inlet manifold, all in very good condition.
Curious I started to blow in the pipes to find one off the one way valves not working.
As a trial I blocked this and now no surging revs through every gear nice and smooth.
This might help someone