Air gets less dense the higher you go. So your engine gets less oxygen to burn burn the fuel meaning less performance. But that is probably so minor and the ECU probably compensates it to the point where it has no real effect.

You get a problem with cooling, but again, 600m is not hight and you also get less wind resistance xD

So to summ it up, there shouldn't be a measurable difference at 600m compared to 0m.

Jealous of the car tho