Ends up being that the head gaskets on the car just gave up the ghost on the dyno, they had progressively gotten weaker since the last race (runs were off by a .10, which now explains it). New gaskets are on and I'm going to re-torque them after a few heat cycles, car feels much crisper now. Not sure when I'll make it back to the Dyno (going to be moving in a couple of weeks), but should have some numbers in the near future...