have you tried being a little more gentle mate? i had the same problem with my ST200 not long back.

was fine when missus drove it but not when i was giving it some stick.

scary when it cuts out after 130 on m6 ill tell you that for nothing


anyway turns out i was just being too harsh, easing onto the throttle made it run sweet as.
to solve my issue i just sold it and bought a cossie. got a heavy foot me lad

cheers darren.