I talked to some people at work and they all agreed with you that it was the fuel lines collapsing. I'm ok with that. and eventually I'll be replacing the valve springs when I install a new camshaft anyway, but if it was valve float it wouldn't stall the motor until I let up off the gas. My understand of valve float is that at the top end the valves aren't closing properly and there will be missing and maybe even backfiring.