Troubleshooting help needed-AC pressures

Not reading every post, i can tell you how I fill my R290 system (R290 (also known as hydrocarbon or HC) refrigerant, which is natural, non-toxic, and free of ozone-depleting properties. Approved in 2011, HC has a low GWP and is one of the most climate-friendly and cost-effective refrigerants available)

Ill start motor and turn on AC, I put the manifold on the low pressure port and read the gauge. Sometimes it will be low or as high as 90 psi but don't let that fool you it will drop to almost nothing when the compressor finally kicks on. I'll open supply side and let it idle for about 10 minutes and then make it a high idle for 10 minutes if needed to pull about 55 psi at 90F on the low side. That is usually all it will need to blow 50F or lower out the vents. Any more doesn't help. The gauge on the R134 bottles have a ambient temp compensation so you dial I the air temp and it will tell you where full is psi wise. I don't have an R290 guage I just use an old manifold I got for 10 on Craigslist but I'm sitting here idling in my R290 filled truck and it's 80F outside and it's nice and cool in here. I fill it about once every 3 months and could care less if I vent R290 as it's only propane!