Loss of power / turbo?

Hi,

I have an N reg 1.8T, about 6 months ago the turbo blew, have had a long running saga since. I had a new one fitted by my local garage, this turbo was faulty so they replaced it with another then a bit of exhaust blew, then the next bit blew, both replaced.

Now I have a problem when I accelerate hard, if I stick the pedal down the car suddenly loses power and sounds / feels like something is about to snap, if I take my foot off the pedal and apply again lightly it continues fine. The garage first fitted a new "temperature sensor", this didn't fix it, they have just fitted a new "diaphram", this hasn't fixed it either - they are now scratching their heads... They can replicate it but it doesn't give out any fault codes.

Edit - Thru looking at other posts, I don't think its the MAF problem others are having.

I confess I don't really know much about engines in the slightest but if anyone can suggest something I can suggest to the garage I'd be extremely grateful as this is driving me mad now! Is this time to take it to Audi? I've already spent a fortune so would really rather not....

Many thanks,

Nick.