Post your email address, or send me your email address in a private message. I've got a real clean 89 NA i can send you some pix of how all that goes. Your 91 will be the same if it still has the factory engine and factory Inj Pump.
there is a contraption attached to the fuel filter looks like a canister with what looks like an egr valve vacuum pot as well as an electrical plug? is there some better source for fuel system info on these cars
The parts you're talking about are for the altitude compensation device. Its vacuum controlled and has an electrical plug. Mounts on passenger fender apron. Its better to disable it unless you live in real high elevation.
If you buy a new fuel filter, buy one for an 85-87 Diesel.
They just have an inlet and outlet.
88 89-92 has the preheat feature with an extra set of inlet/outlet for the return lines.