I've always found it's how violently you lift off that causes the oversteer. I use mine as a rally car, and it is dead handy to be able to get a touch of oversteer when you want it. Just give it a bit of boot and then snap the throttle shut. If you want to reduce the lift off oversteer, try being in a higher gear, or keeping your foot in a bit more (scary though!). I'm not sure if the cup is more oversteery than the normal 172, I have read it is, but haven't driven both so idk. Tyres make a big difference too, if you have ditchfinders on the back and pe2's on the front that will cause it.