I have a 454 in my Nova . Holley 750 vac. torker 2 cam and intake ,headers,10.5 to 1 comp.. The problem is I seem to be getting excessive valvetrain noise . I also get a miss and pop occasionally . Could I have a bad lifter ? I adjusted the valves a short time ago and things seemed better. Now the miss is back . anything over 4500 and it really misses . It used to pull all the way to 6500 with no problem. would appreciate any help