ive got the exact same problem with mine, however i think its an early msd driver in the ecu, the rev counter wouldnt work as it was, i tryed the 4x4 clocks didnt work, tryed the mod on the pcb and didnt work, ive managed to get the early type clocks to work by wiring the tacho straight off pin 26 but only runs half speed, wont run at all of pin 21, the SECS monitor will only ran at half speed too

was going to try the diode mod but has anyone got any pics of how to do it? i know the diode wiring diagram only i dont know what wires the diodes are ment to come off!