can I get an vw expert to help me find out what is wrong with my car?

Hi,
I am having problems with my 2003 jetta 1.8T. everytime I accelerate hard my rpms skip, and I find it hard to accelerate, but when i accelerate light it's fine. When I drive it in the rain I lose total control of the Rpm even when i accelerate lightly. Can you tell me what you think the problem could be? I already replaced my transmission, so I know it's not that. The symptoms are almost similar as if it was a transmission problem.