[ranger22]

I drive a diesel regularly (although its a diesel truck....duramax). I've noticed that in cold temperatures, once my engine is warmed up, it will make more power. However, diesel engines burn cooler than gassers, so it sometimes lakes a long time to get the engine temps up. Also, on my truck (and I assume the case is the same for the TDI's), there are fuel timing and quantity tables that vary depending on altitude and environment temperature. On the colder (and high altitude) tables, the timing is retarded relative to the normal operating timing in order to protect the engine. This will result in a reduction in power. Maybe this is probably what you are experiencing.