'98 Olds CES light, stumbling

'98 Olds LSS, 3800 N/A. Again.
Currently my CES light is on, throwing a fairly constant P0300 random/multiple misfure and an occasional P0442 small leak in evap system.
On the way home today at roughly the same time a P0442 popped up the engine stumbled badly for a second while cruising at a constant speed on the highway and the 'check oil' light came on for a few seconds. The oil level is right at the top and I've already done an ignition tune-up (wires, plugs, even coils and ignition module). Gas cap is recent and tight, and there are no obviously broken vent or vaccuum lines. According to my Carchip logger the P0300 is popping up every trip and the P0442 is only once in a blue moon.
Obvious questions: What would cause the P0442 at cruising speed, AND cause a stumble AND 'check oil' light? And what are the odds that it is related to my P0300 misfire? I suppose my next steps are to look towards the EGR and/or injectors for the misfire but that's just a baffled shot in the dark.
All of this while my ZJ is stuck in the driveway waiting for a water pump and rad. Great, just great.
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442 is not affecting the misfire, focus on that first, low fuel pressure, dirty injectors, the usual list of suspects.

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It seemed like an odd coincidence that P0442 would come up at the same time that the engine stumbled badly. Fuel pressure is an even 50 psi after priming the system a couple of times, not running. In range, if on the low side of the scale.
For the second time now the CES light went out on it's own. Just pulling out of a parking lot and it went out. It'll definitely be back, but it leaves me confused...
Since this thing doesn't have an oil pressure gauge, would it be likely that a flakey oil pressure sending unit would cause my odd 'check oil' light problem? And possibly the stumbling problem, assuming that it's trying to cut out if it detects low oil pressure? Of course I need to verify that it doesn't actually HAVE low oil pressure...
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To update, the fuel pressure with the system primed but not running is 52 psi, running is 42 psi, running with the regulator vaccuum line disconnected is back up to 52 psi. I replaced the fuel filter since I had no idea how old it was, no change in pressure readings. I also cleaned the EGR valve while the plastic cover was off just for the hell of it, and replaced the oil pressure sending unit hoping that it's related to my occasional 'check oil' light. More likely to be the oil level sensor but the parts store was useless on that one and the pressure sensor was cheap.
All of this resulted in throwing the same two codes on the next trip, P0300 and P0442. What's left for the misfire, injectors or the crank position sensor? If it was an injector or two, wouldn't it throw a code for that cylinder rather than a 'random misfire' code? Aside from when that 'check oil' light occasionally pops up, there really are no drivability problems. It feels good and strong although it does run fairly hot.
Any ideas?
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