SBF, lot of cam [242°], 10:1, Holley 1850 [vac sec], timing 18°initail-36°total in by 2200, rear gear 4.11. When decelerating in gear everything is fine until engine rpm goes below 2000. Bucks the most in fifth gear, the least in first. Does it more now than used to in the past as best I can remember. Any clue?