There are three relays located on the top of the firewall on '88 and '89 models. One is for the brake pump, one is for that ABS and the other is for the fuel pump.
The '90 model only has two relays located on the top of the firewall. One is for the brake pump and the other is for the ABS.In 90 the fuel pump relay was relocated to the interior fuse/relay block.
Sorry, I don't have information about the location of brake relays on '91 models.
Fuel Pump Relay Location 1988-89 models