Help! Problem with my A3!

Hi all,

Have just taken delivery of my 2004 A3 2.0 TDI Sport (140bhp), with 58000 miles on the clock. After leaving the garage I accelerated and the car stuttered, missed a couple of times and then I lost almost all power. There were no warning lights but I could hardly pull away from the traffic lights, due to a massive loss of power.

Breakdown company came and diagnosed a fault code saying that the waste gate had been stuck open. The car was chucking out a lot of light blue smoke. When the car got recovered to a different garage to fix it the next day, it was driving fine again but still smoking. The garage have checked the turbo, cat and wastegate and found all to be operating fine, but the car is still puffing out this light blue smoke. The garage are stuck as to what it could be but it is clear that something is wrong. The only suggestion I've been given is that the car may have overboosted at some point and caused some damage to a part of the engine.

If anyone out there can advise me on what they think this could be, and how serious a fault it is that would be a big help. The closer in time it is to me buying the car the more chance I've got of getting them to foot the bill for fixing it!

Cheers,