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Since you didn't provide a link to the other thread, I'll just be guessing as to what advice you have gotten or diagnostics you have performed.

My first guess would be a problem with the fuel pressure regulator. Either a bad diaphragm (leaking) or too much fuel pressure. Not too difficult to diagnose, you'll need a tee fitting and two quick disconnects to tee into your fuel supply line. OH Yeah, a gauge to mount in the tee. I don't know the Triumph specifics but almost every fuel injection system these days runs at 3 bar or 44.1 PSI.

Second would be a bad O2 sensor. Shouldn't really impact startup but once the motor is up to temp, the system will try to run closed loop. If the O2 sensor is not giving good cross voltages, or is lazy, it could drive the system into a default map which normally is too rich as a protective measure.

Finally, a bad TPS sensor or one that is improperly set could cause this behavior. Check TPS voltage at idle and then a sweep of the voltage across the full range of throttle. Again, I"m too new to the Triumph to get into specifics but, when a ham fisted tech broke my TPS sensor wire on my Blackbird, the bike ran so rich for about 100 miles that I got about 8 mpg. Then it (the ECU) decided to ignore the TPS sensor and run off the maifold pressure sensor. Got my home (300 miles) and I pulled the tank and found/fixed the problem.
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