Yep. That's it. Fuel pullover through the squirters. It does chronic things to mixtures and afr as outlined in old mates you tube video.
It turns the accelerator pump squirters into a fuel injector. They just go open circuit. It's one of the most bizarre things I've seen on the dyno. Had a 2 barrel and 4 barrel crossy both do it. Last time I was at Boetchhers on their hub dyno, Brenton their main brain and engine dude couldn't believe it. He actually made me run the car up a couple of times so he could video it. It's not something that occurs on their big dollar, US sourced v8's. It actually does occur on very high revving v8 engines.