I bought a used 350 MAG MPI last year and it’s had a gremlin since I’ve had it. Below is a little bit of a back story. Any help is appreciated.

Long story short, I bought the engine used last fall. Drop it in fire it up and check timing. All is well. Has good oil pressure and idles fine. Get to the lake it wants to surge in and out getting on plane. Once up it runs good.

Check fuel pressure and even though it appears ok it was a touch low (don’t remember the spec off the top of my head) so we replaced the pump and regulator. Fire it up and pressure is great.

Lake test again and it’s the same if not worse but the cables seem to be out of adjustment and i start suspecting the shift interrupt possibly. Get cables adjusted by local marina and they load test it on a prop shaft dyno and said it ran out great. We then winterize and park it for winter.

Now we are at today. Fires up great. Idles great, started surging on fast idle but then seemed to clear up

Also showing a low oil pressure indicator even though the mechanical gauge in the dash is reading good oil pressure.

i believe there are 2 different senders. one for dash, one for computer.

sounds like you already replaced what I'd suspect. Fuel pump and regulator. I have 2 350 MPIs as well. 2001.

I haven’t replaced the oil senders yet. I’m leaning on one of them being bad or having bad connection and it’s shutting down the fuel when it intermittently glitches

I think I read about this, if oil pressure is too low it would cut the fuel pump, but I'm not 100% it applies to this engine. But worth a look!

I ONLY use OEM parts on mine now, if you're buying parts. I chased what I thought was low oil pressure for a while with new parts, and only once I put OEM senders on both engines did both match dead on. NO doubt it costs more, for what looks like the same part. But I'm tired of chasing problems on top of problems... if I know its an OEM part, it seems much more likely to behave like I need it to.

Just for S&G's, check the wiring going to the fuel pump. My starboard engine was doing that and I found out the previous owner rigged a splice for the positive wire that would come loose and then settle into place when I got on plane. IF he were present when I found it, I'd have had to kick him in his junk and then send him on a one way bus trip to Detroit.

I would try rigging up a fuel press gauge to fuel rail that you or someone else can monitor while attempting to plane out.
It is a factory tune on a bone stock eng right?

Also good to know if fuel pressure drops quickly after fuel pump shuts off. If so, you may have leaking injectors. Leaking injectors are usually noticed when warm eng is shut off for 10-15 mins then restarted. If leaking, eng will be "flooded" and won't want to restart readily.

Update: swapped the oil pressure switch and the low oil pressure code has gone away. It says no codes present on scan tool but the scanner also says the check engine light is on and it shows fault switch problem. This all with KOEO as well. I’m not running it on the hose yet

BTW...looks like one of the older RINDA scan tools? How much does one of these run, for sheets and grins?