A/C gets colder as I drive but at idle it stops blowing cold like it should

I know I was here recently about finding the evaporator and expansion valve, but I have this question that might help me understand whats going on. So I changed out the condenser and A/C compressor both new.
i filled up the Freon with one of those gauges I bought from Napa. I got it filled up but not to high just to where my gauge reads full. Anyways A/C compressor goes on, cooling fan is spinning and A/C is cold. Although it's not as cold as it should be and it does get cold like it should when driving, but as i'm idling it will get a little warmer. Now just to be clear this was the reason why I changed out those components with newer ones. A/C had just the right amount of oil. So i'm stuck here thinking maybe I still need to change out the expansion valve and evap. Any suggestions as to why this problem might still be happening?