Thanks for the replies, I've replaced the DV more times than I can count, there's a Rev D in there now as I was sick of swapping the diaphragm Rev G's out, perhaps I've melted the plastic piston, lol.
It pulls well midrange, very laggy low down, where as it's always been ready to go at low revs, its caught me out a few times now... Possibly pipework... Think it needs good look over, Dv, pipework, cam follower, real time scan...
Noticeably this has only started since I did the last oil change a couple of hundred miles ago... No oil leak, oil level fine... Hmm.