Just rebuilt a 600 liberty cleanfire, it ran fine for about 2 hours. We shut it off and then it would only run on 1/2 power and will continue to do so. re adjusted TPS, checked stator, fuel filter, put in new plugs and it still only runs on 1/2 power. Any ideas on what this may be?

Intermittent issues can be a pain to track. Did you check for any applicable trouble codes, before you replaced anything? Your obd 1, you should be able to check for some codes using the check engine lamp on the dash. You would use a jumper wire between terminals a & b at datalink connector under the dash. Turn key just till dash lites come on, the check engine lite starts flashing, you count the flashes to get the codes, your looking for two digit codes.
Before replacing the fuel pump, I would have checked proper fuel pressure. If you have tbi fuel injection, 9--13 psi, plus you can see fuel injector spray pattern. If you have mfi fuel injection, 35--38 psi.
Can you check if system is running rich or lean?
An intermittent rpm signal will drive you crazy, if that is the problem. That signal comes from distributor.

crank angle sensor or airflow meter/map sensor

Check your Air Filter, clean it out, check for obvious blockages. Change the filter if it looks well used (look for excessive dust or color change on the inner part of the filter) or obvious wear.
Check for other blockages around the air filter inlet.

Check the spark plug, just change it for a new one so that eliminates that possibly.

Check your fuel filter and replace if needed.
Check the fuel tank for corrosion or dirt in the fuel. Empty it out, Clean it and add new fuel, be sure you have the correct fuel.
Check your Air / Fuel mix adjustment screws on the carburetor.

Hope that helps a bit
Good Luck

may be a thermostat working intermitently , water pump the same or overheating, keep a look out for anything that is unusual

the pressure switch is bad

Sounds to be electrical problem, check the battery connections, it may be corroded. If its corroded, take a sponge of water and place it to the terminals for a while , it will eat up the corrosion, clean it wth sand paper say a grit of 400- 600 and refit the wires to thte terminals.
Hope this helps!

sounds like you may have it wired to a continuous power source vs one that shuts off with the furnace. The most common wiring is red to C & white to W

sounds like the crank sensor do you know if you have spark now if not could be an ignighter.

This sounds like a problem with the ignition switch. You should get this examined ASAP.

oil level is low???