most common sources are either the 02 sensor wiring is melted or the wiring going to the egr.
id check those places first.
after that, go thru the wiring diagram and unplug everything that +b goes to (isc, vsv, 02, egr, etc).
if everything +b goes to is unhooked and the fuse still pops, try unhooking the main relay (round silver relay in main engine fuse box) and see if it stops popping. may also try the main circuit opening relay that is under the dash on the pass side kick panel.
after you look at all these things you can determine where the problem is and take it from there.
Though the thread is probably dead, I had a similar problem with my 87. The wiring harness kept melting it's sheathing off on the EGR and shorting the ignition fuse. A zip tie and some electrical tape does the trick fixing it.
I had this happen to mine and the short on mine was in a hard place to find. Location was in between the gas tank and the body of the car where the fuel gauge wiring harness. With a short on the EFI circuit you can't retrieve a problem code from the diagnostic port. Short circuits are hard to find sometimes.