Ok, I have been dealing with this problem for two years now on my wifes 2000 1.8 turbo. When the outside ambient temp is under 70 degrees the car drives fine. However, when it gets over 70 degrees the check engine light comes on and throws a vag code of 16795 and a 16963. Some people tell me the ecu is in limp mode as it will not make boost over 3000 rpm. When you lug the engine from idel to 3000 rpm the turbo comes on fine and pulls good, however, as soon as you reach 3000 rpm, the boost is dumped and the engine is all on its own after that. I have done some research and I am finding that a n249 valve might be the source. If any one has any ideas here it would be very much appreciated. The fuel pressure is good and the engine runs fine, just no boost or power after 3000 rpm. When it gets cold out it, the engine will go back to normal. Is there some type of fail safe in the ecu when it sees a higher temp to eliminate detonation that it dumps the boost? Please help. Thanks!!!