First off,
The MPS works with the cylinder head temperature sender to calculate how long to open the injectors. If the CHT is bad or disconnected, the engine will run very rich all the time.
Check the CHT sender for resistance (I think 1000 ohms at room temp) and make sure it's connected ok. It's above cylinder #3 intake tube.
Likewise, if the MPS is leaking air, it will always call for more fuel. Test it with a brake vacuum bleeder pump if you have one. I bought one at Harbor Freight and have gotten a lot of use out of it.