I'm using cans of pure r134a. always purge the line and account for loss while purging, while on the scale between can changes and converting oz to pounds. I'm not sure at 1200rpm. But I can tell you I dont see those kinds of pressures on the high side. I was seeing around 125 high side idling and not much change when reving to 1000rpm. This Tahoe was originally destined for upstate NY. I live in Missouri where during summer months temps and humidty is high. What is this enhanced cooling package you speak of? Is it a specific RPO code for say trucks that stayed South?
K5L is the RPO code. You will know when your fans go to high, they roar loudly and you can feel it walking by the front of the truck.
Your high side is too low. You were saying it was 90 degrees outside? At 90 ambient your high side should be around 170-220. Sounds like either compressor is not working properly, possible restriction in condenser as in metal (check for high line to be hot all the way to the gauge port, after that it should be cold at orifice) , possible rear AC expansion valve stuck open, or undercharged system.
When you rev the engine the high side should go up and the low side down. If it doesnt then compressor is bad.
Idle will always be the warmest so mid 40s is good on high blower. At highway speed mine blows high 30s around 38.
At this point I would add a few ounces of 134 at a time and watch the pressures, if undercharged your low side will stay almost the same and the high side will go up......temps should drop.
