brilliant post Nola,iv never seen that before....sweetHi there... where yat?
As you mention, there have been a "few" issues already adressed ( sounds like mine ) sounds like you need to go through the air intake syst from the filter, boots, then carbs...
My bike ran like a turd initially. Cleaning the filter(s) in the airbox and un plugging the crankcase breather did wonders ( ran on both cyl ) Fixing the airleaks also made things much better.
The big winner was cleaning my carbs last week... the little decelleration pops I figured were normal are now 99.9% gone.
You could have so many small issues combined or one big one... it's impossible to guess. A good cleaning and maint of air syst. and carbs won't hurt anything and may bring it around. most if not all cx's either have had, or badly need this TLC...
Reading your sparkplugs is a good initial diagnostic.
Added: from the web...
AIR CUTOFF valve - Enrichment Circuit
You're blasting down the road and you see a hairpin coming up, so you close the throttle. This closes the butterfly valve. You and your 400 lb. baby (the bike, not the other love of your life), are still rolling with inertia, keeping the engine revs high. Now it can't get the mixture it's trying to suck in because the butterfly valve is closed, blocking the air flow.
To compensate for this there's an air jet in the lower diaphragm chamber that transfers ambient pressure to one side of the coasting enricher's spring-loaded cut off valve. The excess vacuum in front of the butterfly valve is transferred to a drilling that leads to the other side of the cut off valve. This sucks it open, allowing the pilot jet to feed more fuel to the engine, preventing an overly lean condition. (Pop. Pop. Pop.)