Turbo "pinging" noise
 

I have a 2004 9-3 with the 2.0t. 94K miles. I recently had the timing chain, tentioners, guides and water pump chain replaced. Both chains are tight with very little slack. The car runs fantastic except for one thing,

When I accelate and the turbo nears the red line, I get a pinging noise. This happens for a while and then goes away once the car has been driven for a while. Once driven, especially on a long trip, I can hit maxium boost without any noise at all. Now something that is interesting is, that I can get the engine to rev to 3500 - 4000 rpm while in park and not get any noise at all.

When the noise occurs, it comes from the area where the turbo is located. I'm not 100% convinced that it is the turbo, but can't figure out what is causing the ping. Any help is appreciated.

Thanks,

Taget