Rich at the hit is typical for anything that spends time on the brake for sure, never seen it cause an issue like he is having though. I have seen 10-1 fat conditions at the hit. A combination of lots of carb and being on the two step dropping cylinders will cause it. If it was a over rich condition a quick review of video could help confirm that, one would think if it is bad enough to cause the car to slow that much there would surely be signs of it on the video. I think it would need to be WAY fat to cause that. But ya never know I suppose. Only other way I have seen that happen is fuel dumping out the vents that will create a bog for sure and a tell tale puff of smoke, but he says it dead hooks and goes so don't see it being anything like that. Kinda like an intake leak, it should be present all the way down the track, cannot imagine that would repeat from knonw good runs with the extra air. Unless we are assuming it is "sealing" itself with more heat?

IMO most people run WAY to much fuel pressure to begin with, usually to mask an inadequate fuel system. My car is at 4.8 lbs throughout the run. Data logging might certainly help to narrow this down for sure. Would love to see a driveshaft and an acceleration graph for sure.