[nize]

it sounds like the car may have been abused by over-boosting. if you don't know the complete mods that have been done, you should go through it all and find out before you start troubleshooting.

i'm assuming the stock boost gauge goes up to the max 2bar so you don't know how much it goes beyond that. do you have an aftermarket boost gauge? you should MAKE SURE you are not overboosting before you get on the throttle again. i'd hate to see you destroy the motor and find out the hard way why so many of these cars end up being sold for cheap.