This same issue has happen to me 3 times. It is a documented occurrence with Triumph. There is a bank of sensor tubes under the fuel tank, and one of the tubes has come off or is loose. According to Triumph it is caused by a back pressure from the air box, and in some cases can be cured by adjusting the timing. My shop did just that and with a replacement of the banks and some of the tubing, it has been 3500 miles since it last happened.