Hello and greetings from the US!

I have an 08 Supercharged and have had a strange a/c problem pop up that I would love some help with. Nearly all of a sudden the a/c has stopped working as well as it should. It will often run just fine (although still doesn't seem as cold as it should be) when idling but as soon as I start driving there is a 10-15 degree (Fahrenheit) temperature rise that will sometimes stabilize back down to where it was but sometimes will stay 7-12 degrees higher than where it originally was. Compressor seems to be engaging fine and the blender motors seem to be working as well.

I bought a low pressure line gauge as this seemed to be a low coolant pressure problem but it was holding steady at 50 psi. High pressure line seems to be warmer than it should be but I'm not really HVAC privy so it's hard for me to say.

Any help would be much, much appreciated. Thanks in advance!