I agree with you TDF and Ben,
I think historically, the Porsche power claims have always been a bit too conservative.
Ferrari? I don't know honestly.
My friend who works there told me the engines of the Maserati have always done about 400 hp instead of the claimed 390 but for marketing reasons, couldn't say it was equal to the 360 which was still on sale then.
F430, really don't know. But looks like it does have the 490 hp claimed, then again, that straight line race you witnessed seems to indicate otherwise Ben.
I'm not too fussed, I'm more fussed about weight claims like tdf, it seems universally that the Stradale is much heavier than the weight claimes, maybe the F430 too?
And the 997S too, about 40 kgs more than what the manufacturer claims.