Distributor CMP Offset Issue

[wildwilly]

I hope someone has a similar issue that can help with a timing the camshaft retard offset (CMP) and aP1345 issue.

I have a 96 K1500 5.7 ... 280000 total miles. It has about 700000 miles on a replacement GM engine. After about 50000 miles there was a slight ping under load or higher RPM. At 60000 miles I was getting random misfire codes under load. Eventually after throwing parts at it with no change ... I did a full tune up. It did get better but still pinging a bit ... but finally read about the Distributor CMP offset and decided to check it with my scanner and it was at -10. I rotated the distributor, but could only get to -4 before it hit the intake manifold. At the same time I did a compression test and all cylinders were sound. It ran a good bit better, ping gone and no more error codes ... well I decided to see if I could move the distributor clockwise a tooth and reset CMP offset closer to zero.

Since I was pulling the stock plastic distributor I sprung for a Summit Racing billet replacement. I set it back one tooth from the original and reset the CMP and now got it to +1 degree ... within the +/- 2 degree window. It started back up straight away and sounded good, but P1345 is set right at start up. It resets and comes back immediately on restart.

I read you need to re-learn the crank/cam, but another place said this is only on 98 an newer. Do I need to take it in and have this done? ... or do I need to move it back a tooth and live with the -4? I am not sure how it got to -10 to begin with ... maybe being off a bit initially and wear over time?

Thanks in advance if anyone can help.