I had all manner of probs with my '86 8v recently occasional loss of power, missfiring under any load, odd elec probs. Some days it was fine and some days wouldn't start at all. I checked all the usual suspects earths, connections, fusebox and relays, even fuel pump but all was normal. Wasnt until it cut out and everything went dead while driving that i realised it had to be the immobiliser which was at fault. It cuts out supply to fuel pump and ignition. The internal relays were faulty and not allowing the full voltage through!! Still, its the only time she's ever let me down. Not bad for 4 yrs of ownership!