This is driving me crazy, cars been running fun for months and has suddenly decided to throw it's toy's out of the pram. Once the engine is warm when I hit around 80 - (who me officer? oh no I couldn't have) motor starts to misfire, back off and it stutters for a while and then clears if I cruise at 60 ish. It struggles under load so hills make it miss as well. I did have this a couple of years ago and it was the crank sensor wiring. So I've replaced the crank sensor, plug and wiring but problem persists, I've done plugs and leads and coil is about 18 months old.
Interesting in that the crank sensor wiring I took off had no shielding but worked no problem

Carbs have neen stripped and cleaned but I'm still inclined to think it's electrickery related Current set up is blacktop Zetec running GSXR600 carbs, and megajolt on base map. As I say the motor has been sweet as a nut for the last 6 months and I haven't tinkered with any settings so I know there's summat up! Ideas?