God knows whether this offers a potential explanation, but were the cars that ran later in the day the cars that were achieving silly figures?
E.G. Mine was towards the end of the day, Dom T's was shortly after mine, as was VW Rascals. Caz's was late too.
Dom's ran higher than expected, and VW Rascals stock GTI ran 230hp if I remember correctly?
Although saying that....there was another standard GTI that ran quite early on that got 230hp.
Dunno?