Allthough I had a stutter at high revs months ago I got that sorted, But mine has just started doing the same as yours.
One thing I have realised is that when pulling off form standstill if I rev it to about 3k revs first it's fine, only below 3K
It can run rough on tick over so i got a bit of water and after a few seconds of the engine running dripped some water onto each downpipe one at a time and it is No 2 cylinder not firing prperly...as the water didn't fizzle as you'd expext on a hot down pipe ( does that make sense )
So for me I know it is something to do with No 2......maybe worth a try see if it's one cylinder playing up? I just gotta get time to balance the carbs to see if that sorts it .
Andy