Sounds like maybe a power valve busted or started leaking.Check the valve,or if you don't run one,check that the gasket for it isn't leaking.I prefer the teflon rings over the paper gaskets.Also,make sure the gasket didn't fall off center of the valve/plug and let it leak.Not that hard of a mistake to do,especially when making those track-side thrashes.But that is just one of many ways to idle too rich.Check the little things,too.Idle mixture,fuel pressure(again) and leaking needle and seat can force fuel in enough to cause that problem without actually loading up.Just my opinion,but that's where I'd start.