1983 Other Mitsubishi Models

'83 Mitsubishi Starion, engine stalled while driving, then started missing/backfiring, running very rough. Started up a few days later, the same but no smoke (but still not driveable, revs up and down). Then next time I started it up lots of smoke, now won't start at all.

Engine is 4G63B intercooled 2L turbo (EFI). Bought off a dodgy little bearded car dealer, then the day I drove it home, it did this. He did mention that the balance shaft was out of sync, which caused some vibration. But I'm guessing that's not the problem now. Cambelt was done very recently.

Nothing seems visually obvious under the bonnet, but I didn't look at it for long. I suspect something to do with the turbo/EFI, or worse.