fuel system swap
#4
It may run fine but it's not optimal. Just like you can run a 5.9 engine with a 5.2 PCM which a lot of people have done but it will run lean. The '93 PCM want to see a change in fuel pressure via the vacuum supply to the fuel pressure regulator. When you get on the gas, vacuum goes away causing your fuel pressure to go up. Your '94 returnless fuel system's fuel pressure stays static so when you get on the gas, fuel pressure stays the same and you are going to go lean. Either get a '94 PCM for your '94 fuel system or get a '93 fuel system for your '93 PCM. You can run a '94 PCM on a '93 fuel system (just don't hook a vacuum line to the fuel pressure regulator) with no ill effects but you can not run a '93 PCM on a '94 fuel system without any ill effects.