hello I’ve got a 2013 Delphi gv250. it idles and revs great with both cylinders but once you start riding the first cylinder will give out. there is a sweet spot around 35km in 2nd gear were everything rides smooth and both cylinders feel strong, but any loss of throttle at any point immediately kills the engine. You could be anywhere from 5-9k rpm’s but if you let off the throttle the engine stops.
New ECU changed nothing