what will happen if it wasn't installed straight up?

 

If it was installed retarded it would move the power band around as would advancing the cam. ie advancing gives you more mid lower with a grind and retarding moves it up a bit. (or is it vice versa...lol, been so long since Ive done it). But that is kinda low for the peak, You know when I look at my dyno sheet it only was putting out a little over 300 hp from 5 to 5500 and the peak as said was a few hundred past 6000. since your A/F ratio is good the valvetrain is a possibility. I know when I was younger I had a 79 T/A and it had some weak springs and it would just like hit a wall around 4500 rpm. I just marked it up to something else until I had the heads redone because of a blown head gasket so I put in new springs and it would then go on up to 5000!

 

but when i had my bent valve replaced, he did a pressure test on every spring and he said they were all in good shape. He also cleaned everything up on the heads and did the whole 9 years.
i am just wondering if my tranny came into play here.