I think the pumps relate to the mk5 I've never heard the issue with the 6.
Part from the tensioner failing there isn't much else, some people have had issues with the inlet manifold however most of these have happened post stage 1.
Not saying the mod has caused it but a weak manifold the extra power has probably pushed it too far.
With regards to negotiating on the tensioner I think you probs will be wasting your time, there is nothing wrong with the tensioner *cough unfort it's a risk you have to consider, many are fine some arnt...
UBER TIP: if it sounds rough as sh@t when it first starts up, walk away, in fact leg it ....