The compression from 8:1 to 8.6:1 would make loads of difference, people complain how the responsiveness is shit with low comp and with the low comp engines people were going down to 7.6:1, that is only 0.4 difference where as 8.6:1 would be 0.6 difference

Also do you have adjustable pulleys?? cam/valve overlap will make a difference, just because all your markers are lined up doesn't mean this is the best your engine will run things can still be tweaked, ignition timings etc.