[FrankenDesmo]

Forgot to mention earlier - I appear to be running 175 mains, which seems a bit excessive given that the workshop manual states 140!

Edit: aaaand the stock pilot air jet is a 1.4! This bike has definitely been fiddled with. I'm going to get another 1.3 as is already in it, clean everything up and put them back together. The needle jets (emulsion tubes) look like they're quite round so probably don't need replacing (although I may decide to yet). I suspect it's been jetted following the exhaust and airbox mod, but the engine could also have had some work - who knows. I'll also take the intake runners & rubbers off and give them a thorough check for any air leaks.