Hi Mark, Although I don't have an MBE I have heard of the coil drivers failing on ECUs - I vaguely remember having a similar issue with an Emerald. I guess the easiest test is to borrow a known good ECU, load your map onto it and test. The fact that it's a pair of cylinders with the problem certainly points at coil driver. Looking at the pinout, cylinders 2 and 3 are off pin 18 so that would certainly make sense with your symptoms. Shaun