Pretty much everything. It understeers then massive oversteer, too early and much on the throttle and it'll bite your head off...
Just read that there's a McLaren F1 "Stealth". Is that one you can win and is it a premium car? If yes, then perhaps I better sell mine to get some cash back to progress in the game and wait until I win that one?
All Stealth versions are bonus cars given out by various retailers. They are basically the sames cars but with a stealth paint / all black and they are available from the start for those with the pre-order bonus code.
I haven't driven it yet, so I don't know about the handling, but it's a very small car ... It has some of the craziest stock accelleration in the world, so the kind of behaviour you're describing is to be expected. If you haven't done any tuning to it, I would start with getting soft racing tires for it as that should be a massive help. Another TCS like trick is to change your gearing so that you get a little less traction in the earlier gears. It makes you a bit slower in theory, but while grip is the limiting factor it matters little.
Personally I passed on it because it isn't a car that is really called for by a specific race type. I found the Gallardo much more useful for that purpose (the 'basic' one), which I tuned a bit and handles very well (4WD helps) and is eligible to the Gallardo race on Rome for instance. That also gets you the (1974?) Countach which you can use in various events limited to cars before the 80s / termed classic.
It took a bit of work (the Indy race I managed first try with some blocking, but for the other one I went from 9th to 5th to 2nd to 1st, with a few restarts - I could use the practice though and it got me to level 22
), but I managed to beat Like the Wind with the Furai, as I expected. Cool
I also beat the Schwarzwald B Cape Ring race with the SLS now (didn't end up using the R8 that I bought yet, wanted to see if I was up to the challenge), which was a nice challenge also, had great fun and also took a few attempts. I left TCS at 5 but still had to be pretty careful not to spin out that SLS coming out of the sharper turns.
I even tried one of the JGTC races with the Furai, Tokio, and I just blasted away the competition completely. That Furai is a mighty beast - handles great, fantastic brakes and grip, and you can win a great number of races with it.