A/C on my Daytona not working properly

[DoubleD]

I added a brand new expansion valve this year.

[DoubleD]

Update:
I decided to forgo having the shop work on my car anymore for this, I went to Autozone and found out they rent the A/C tools again, I picked up the manifold gauges and electric vacuum pump. I picked up a manufacturer rebuilt compressor for the car off ebay (PN#77614). I had to swap over the coil, pulley, and wiring from my old one, but everything else worked as it should. I replaced the compressor inlet o-rings. I then vacuumed out the system and let the pump run for 1 hour, then I let it sit for another 1.5 hours with the pump off, system help vacuum without an issue.
Now I went and charged it, I added 2.25 cans at the recommendation of a trusted source. Gauges were reading 30 low and 280 high, vent temps were 51 degrees on a crazy humid 87 degree day.
Did a lot of looking but what should my gauges be reading? What is a good pressure to strive for on the high and low? What should my duct temps be?
This is my first attempt at A/C and I want to do it right! Any help is greatly appreciated. The system is not stock so the original fill value is not correct anymore.

[Force Fed Mopar]

Generally speaking I always saw around 250psi high side, if everything was working as it should. But you're probably pretty close to being right, I'd run it a few days then check it again.

[DoubleD]

Should I be checking the pressures when the car is relatively cold, but running? I had the car running at least 20-25 mins last night with the A/C on high, I can guarantee in that time, the condenser heat soaked and was getting hot. I'm guessing on a cold running engine, the pressures equalize pretty quickly after start-up.

[83scamp]

Here you go:

http://acprocold.com/faq/r-134a-system-pressure-chart/

Generally from what I've researched, you want the interior hot, and the engine warmed up to check pressures. Because that's where it will run at. Doors closed, but windows down, so there is a load on the system.

[crusty shadow]

We're saying the same thing, the system has to be turned on with the engine running to make a gauge reading.

as another mopar trained tech i have to also politely disagree. connecting guages without the engine running can tell you quite a bit about what is going on with your A/C system
connect gauges with engine cold. both gauges should show the exact same pressure and should be within 4 psi of ambient air temp if the system is properly charged- eg- at 70 degrees you should see 70 psi + or - 4 psi.

also we just had one wed that had given 3 other techs nightmares. problem was A/C would start blowing warm at random times. replaced compressor, replaced reciever drier twice, when it got to the last tech we were able to get the problem to appear while the car was in the shop. shut the car off and looked at the gauges- 35 psi low 380 psi high.pressure between high and low side were not equalizing- there was a major clog in the system. the ac originally didnt work when this car was traded in, problem was a failed compressor. turns out that compressor sent shrapnel all through the system- we confirmed this when we vacuumed down the system and opened up the inlet for the condensor- tech stuck his finger in and it was covered with metal flakes when he pulled it out. debris was clogging passages in the condenser, when the a/c would be shut off it would allow the clog to move enough for a/c to work normally again.
again the problem was so intermittent, pressures looked normal even when the problem was occuring, but we could not really find the problem until we looked at the gauges with the engine off.

[HSKR]

Odd question I know, but never saw it mentioned before. You did add the proper oil and correct amount after replacing compressor right? You said tech said compresssor was getting hotter than it should, which to me might mean it's not being lubricated properly.