6.0 low power, gauges acting weird
Went to Phoenix today,about 80 miles. Truck ran fine, didnt notice and problems.Stopped at Harbor Freight for 30 minutes, came out and forgot I was in the diesel and just started cranking the engine,didnt wait for the glow plugs.It cranked longer than normal,started and died,cranked, wouldnt start, cranked start and die. all the time the glow plug light comes on for just a second and goes out, seems other lights near it are too.Truck starts, seems to run fine,drive a couple blocks, go eat lunch.Hour later I went out to start, turn key, glow plug light goes out after 1-2 seconds.Turn key off, back on, same thing.Tried cranking, start,die,start die, finally lit off and seemed to run fine.Took that as an omen and decided to cut trip short and head for the barn(home) 80 miles away.Notice at idle the oil gauge drops to nothing, over 750 rpms its above 1/2 way.Under 750 it drops like it was unplugged.Just on or off.Check oil, got lots.No smell on oil, no sparkles.Engine sounds normal,but the oil gauge keeps doing its on/off thing.Convinced its not a real oil pressure issue, or at least hope like hell it isnt and drive off.Low power, runs fine, just not much happens if you nail it.Runs fine all the way home, as long as rpms are over 750 I got over 1/2 on the oil gauge, one rpm under and it falls to nothing.No smoke, no weird noises.Get home use the SCT tuner to check for codes, says I have none.Install stock tunes, turn key, glow plug light acts normal, but truck doesnt start right, still the start,die, start, die, finally go, sounds fine, oil gauge doing same weird thing,same as before.check codes on stock tune, have 2 that are EGR related, and since I have an EGR delete,I expected that.Engine acts like its getting no boost, I have no boost gauge so dont know that for sure. I hear no whistle, or sucking sounds,just put new intercooler boots on.I have had the truck 8-9 months, and the turbo has always made a "whirring" sound.A friend who is on his 4th 6.0 said it was normal.I bought a used turbo and put on, sounds the same.I did a clean job on both turbos and both looked ok. Truck is a 2004,made late,F-350 chassis truck with service bed on it.Weighs about 8800lbs, has a River city Diesel EGR delete kit and a SCT tuner with custom tunes from Innovative Diesel. How do I check to make sure I do have good oil pressure?I'm thinking if I didnt , driving 80 miles would have caused a few new rattles.Something else, that I'm not sure of , but it seemed like when we got to town the speedo seemed to read fast.Girlfriend even said there was no way I was going 40 in 25,I had to agree with her.Now we did just get off the highway at 65 mph so maybe we just wernt used to slow. But it did seem to be 10-15 mph fast, but seemed ok on the highway.Bottom line, oil gauge drops to none at low rpms and low power. What to check next?