1982 XV750 Carburation Problem

Hi Guys. Wonder if you can help me out? Bought an XV750, as mentioned in previous posts, and it conked out on the way home after 30 miles. Green flag obliged and I cleaned out the concrete-like blockages from all of the jets, bowl etc and managed to run it intermittently sometimes on one cylinder. Forked out £160 to have the carbs rejetted, cleaned etc and it ran fine for a few miles then started chugging. Checked the plugs and they were choked up with carbon preventing sparking. Cleaned and started resetting pilot jets and running in between until I had them turned out 3 and a half turns. Still fouling! Did that paper test thingy on the remote Mixture Control Valve. No vacuum throughout the engine rev range from 1000 to 5000. Sourced a used one and tested. No vacuum still but sucks paper in when revs let off!! What's it all about???.

I fitted 2 new standard Plugs as per Haynes and the air filter is clean. Read on a forum somewhere about removing the MCV and blocking off the two vacuum tubes. Is this an option or a total fantasy?? Apart from stopping every few miles it is obviously using a lot of fuel so it's no laughing matter!! And, to be perfectly honest I look a right twat stood at the side of the road tinkering or sweating like a Sumo Wrestler in a Sauna as I push it home in my leathers and Damart Thermawear!!

I have been trying to do this alone but I am completely flummoxed and would appreciate any help you Heroes can offer.

Regards