another opinion is the temp sensor in the DPF making the vehicle think its running too hot - this releases a burst of diesel causing the injector pulse - all i can say is watch this space and i will post an update after my remapper has applied a newer version of the original one. im on hols til 17th but will sort it then
 
Are you sure your intercooler pipes are not leaking boost. It would explain why you only get it in high gears when the car is trying to hold boost for extended periods of time. I remememer reading it is the pipes into the intercooler that blow. Why don't you put some proper clamps on and try it then? Apparently the standard Seat spring clips are rubbish at high boost. Do a search, I could be wrong, but it would be an easy fix if I am right!
 
Sieze thanks for that - it was me who put a post on about the intercooler pipes lol one of mine had loosened but unfortunately it was just coincidence :(