I have a 1991 350 tpi that has been difficult to fix. it runs out of power and then picks up on 4 or five cylinders. what should i be checking?

 

1.How do you know it's only running on 4 or 5?
2. What engine codes do you have?

 

Welcome to the club, rocket.
You definitely need to provide more information. To quote the master: "help us help you".

Define "difficult to fix". If you diagnose it right and find the bad part, it is always easy to fix/replace. If you don't diagnose it and just start throwing money and parts at the problem, you will make some mechanic happy and rich and make yourself unhappy and poor.

A good running engine needs clean air, good fuel supply and clean spark with good timing. If you can find out which one is missing, you are halfway there.

Timing, fuel pressure, manifold pressure (or vaccum), it would be good to know all these.