I have a strange problem with my impreza wrx' 04. Sometimes, seldom, when I need to go fast, on first or second gear, I step in on gas pedal, car go faster and suddenly starts bouncing abruptly back and forth. Today it happened on first gear and I got feeling car wants me to fly out :(

Does anybody experienced such problem ? Do I do something wrong or I have some failure in the car ?

Is it partial throttle or full?

No mods at all.

I think it happens under the full throttle, but can not tell this for sure. It happens so suddenly and strong so I just can not judge the timing of the event.
Idea is to go fast, so it must be full throttle.

I know under partial throttle the car will lurch sometimes, but I've never had the problem under WOT. Sorry man.