Or more specifically, fuse on top of the OVP, is my guess. It's found near the firewall, under the bonnet, on top of a little box between the size of a lighter and a cigarette packet, usually under a plastic lid.
I reckon this because:
A) It very often blows when people jump start cars
B) Without it, it runs very poorly, just like how you describe (although, it mainly effects cold running)
See how you go..
2.5-16v 1990 90,000m Astral Silver
2.0E 8v 1986 107,000m Black