Without looking at the book is it with no1 or anticlockwise one hole as per Lycomings......... may be worth as a long shot pulling the prop of and putting it back on 180 degrees round so blade 1 is where 2 is, if that makes sense, also make sure nothing is touching, eng mounts have not sagged, pipe rubbing cowl etc or even the exhaust where it cones through because they will transmit vibration.
I also take it its not a plug breaking down, timing is spot on etc..... we used to have a rough Lycoming at high RPM and it was sucking fuel past the float bowl gasket, primer leak or induction could too.