I am haveing very similar problems with a 340 j heads port matched purple .450 .455 268/272 670 avenger hp manifolds tti2.5 15.2 1/4 2.2 60 ft 3.23 gear It quit pulling at 5500. so far i found i used a dial back timeing light. bad. it was off. i thought i had 36 total and it was more like 40...