94 Bonneville intermittent start
1994 SE with 184,000 well cared for miles. 80% of the time it starts fine but the other 20% with absolutely no pattern, won't start. The dash lights illuminate, the engine cranks fine but won't start. Sit for 10, 20, 30 minutes everything starts fine. My oil gauge was also bouncing around. The ECM is throwing; PO321, PO225, AND PO1361. I swapped in a new oil pressure sensor, new throttle position sensor (the car had also been surging at idle.) Surging and oil gauge fixed. I had heard that PO1361 was almost always the PCM. Replaced PCM with remanufactured unit, still has starting problems. The car will also SOMETIMES stumble when driving as if it wants to die and the "check engine" light illuminates. A push on the gas peddle gets through it and everything is OK. The "check Engine" light is intermittent and does not come on before or after the starting problem, only sometimes while driving with the stumbling issue.
How do I check for fuel pressure? Might this be the crank position sensor. Does the CPS fail outright or will it linger?