Reliable enough that Jaguar was using em as OEM equipment though hidden. Years ago my friends moms Jaguar XJ12 Vanden Plas editions ignition module crapped out and we cracked it open thinking it would be something gee whiz that maybe we could fix, because a new jag module was insane in cost here in the states. Of course this was in the day before evilbay, and rock auto, I dont think Algore had even invented the internet yet LoL. All that was inside that fancy finned aluminum box w a Jaguar part number was just a GM 4 pin module lol. Heck that car would eat thru Lucas ignition coils until he installed the Accel super stock coil from his 71 Road Runner on it. That was the last coil he ever put on it. LoL.
