A fuel system that old may be going bad. I would guess the pump, not so much your injectors. Though, its not a bad idea to do the whole thing. Get it ready for power in the future while you are at it ;p
I have a fuel tester you can borrow if you need it. (Auto parts stores don't let you rent them). Why don't you replace the tps instead of still guessing. Put it on plug it in, if it doesn't work bring it back. Its not like you don't work at a parts store.