I played this on my PAL PS2 the other day and when you drive in a straight line with the extra grip powerup the cars do some shuffling around, turning a little to the left, a little to the right, and the controller vibrates a little. In Thed's videos and other videos on the net I don't see that kind of movement and compensation. Is the powerup different between versions?

It may be that it is different from one to the other, I have only played on the NTSC emo.

And as you said I myself can't see or have run into the problem.

but do you have a clip of when it happened? and do you play on a emo?

If you have a clip to show that would be cool, I don't remember personally. Rumble Racing will run slower on the PAL version due to it being 50hz, I'm not sure how that would affect (If at all) the in game timer though.