01 6.0 random misfire

[hardhead]

I have a 01 3500 with a 6.0, 168,000 miles. Recently while getting on the interstate it started bogging like it was loosing power and the service engine light was flashing. The light stopped flashing after a few seconds but then idled rough so I checked the code and the only one it had was EGR low flow. I don't recall the exact code but anyway I went ahead and replaced the EGR valve since it has a few miles and now it still does the same thing at times but I get a P-0300 randon misfire. I have changed plugs, wires, fuel filter, checked fuel pressure, and compression. Fuel pressure was 45psi so I swapped the regulator with my Dad's and that didnt help so I changed the pump. Same issue so checked compression and all were within 15lbs of each other, pulled the valve covesr and spun it over, looks like the cam is good and didn't see any broken springs. I drilled a hole in front and behind each cat to check for blockage and one side seems to blow a little harder in front than behind. I was gonna pull the fron 02 sensors but they were stubborn so I left them alone. I drove it with the holes open and it still did the same thing.

[hardhead]

It seems to have pretty good power after the fuel pump change but it still flashes the check engine and it rattles or sounds like detonation at about 4000 rpm's. I also swapped the MAF sensor with one off my sons truck and no change. I have read that a cam position sensor re-learn has fixed this for some other folks, has anyone here had this issue?

[69gmcc10]

what spark plugs did you upgrade to?

[hardhead]

I put AC's in it . I got the left bank front 02 sensor out and drove the crap out of it and couldn't get the light to come on so I am pretty sure at least that cat is partially plugged.

[69gmcc10]

I asked the question because I had similar problem when I installed E3 plugs, random misfires everywhere so I went back to ACs.

before my cats went out I had O2 sensor codes and misfire codes.

Good luck

[hardhead]

Random misfire code only.

[69gmcc10]

How large did you make the holes?

If you think it is the cats, you can disconnect the exhaust from the headers, let the y pipe dangle with enough room for the headers to flow freely and take it for a quick drive. it will be loud and throw codes that you need to clear, but if the power is back you have a clogged exhaust.