The ECU and ignition circuits use fuseable links. A Red link rated at between 9-17A max and a Brown rated at 5A max.

Fuseable links work pretty well and are still available from the dealer or Enginemachineservice.com.

If your going with the blade style fuses I think fasteddy's advice is pretty good. You really shouldn't need anything higher than a 10A fuse. If you popping 10A fuses easily you may want to re-check your wiring.

'87 Raider SWB 2.6T/5 spd - Boxy and boosted.
'88 Conquest TSI - MPI and lots of other mods