A ThumperCarbs 1050 Dominator on my 408 was worth 15hp on the dyno over an OOTB QF 950, but, picked up 6mph and .400 in the 1/4mi. Dom tests each carb and they are right when you get them. Mine got 15 mpg and cruised no problem. Excellent cold starts to boot. That carb is for sale - $1,000 + shipping. I am buying another for the new engine!