You just had the tank off for painting , and to your knowledge it ran well before that . The odds are something has been upset . Is there a little 8mm spigot that comes down out of your tank near where the fuel supply line goes into your pump assembly , this has a rubber pipe connected to it and acts as a breather . Maybe that got pinched or kinked . The electrical sender connection not inserted properly or maybe has some s***e in it .you could also check the hoses that connect to your manifold/throttle bodies . I had the tank off recently and upset one of those hoses and the engine management light came on . The bike wasn't running poorly , but it will if you displace one of those hoses Also a lot of Triumphs have the ignition coil unit fixed into a cradle which bolts to the under side of the frame member that the tank sits on , maybe one of the terminals was nudged . Hope you get it sorted soon .
