[jcfrei]

> These cars could in theory be even faster.

The constraint is not the budget or testing though. You could make much faster cars with even less money if you removed some of the constraints (particularly in minimal car weight, engine size, aerodynamic effects, fuel, etc.). You don't want them to be much faster for safety reasons - if they go much faster then there would be too many situations where the human reaction time is not sufficient to avoid an accident. The Group B (Rallying) competition suffered from too many accidents and was disbanded.