08 6.1 low side 58 high side 300

Sorry Joe, forgot to look in on this for a couple of days.

It is difficult to diagnose a system without pressures. You mention "cycling", but that should only happen when the evaporator temperature is near freezing.

Get the gauges on it, and do a full load test:

Cabin fan on highest speed, doors open.

Engine rpm to 2000. Hold 2000 rpm for 2 minutes to stabilize, and record system pressures while @ 2000 rpm. Record ambient temperature during test, as well as vent temperature.

A system loaded like that should not cycle. If it does cycle, it may be cycling on the High pressure cut out or HPCO. This is a bad thing. Of course if it is undercharged it may cycle on the LPCO... Really need to see both pressures during the test.

Hopefully you purged the air from the charging hose you used to add the refrigerant. In this case, a little dye, oil & refrigerant will not do any harm. Adding 4 ounces of oil might, but most of those cans do not have a lot of oil. In the future, use only pure 134a.

B.