Today I hooked up the gauges to the AC system on a 2003 Jetta TDI. I have noticed an issue with the AC taking taking longer to get cold, but it does eventually get cold. My low side reading was 41psi and my high side was 290psi with the system running. Also, my low side reading after the car was shut off rose to 390psi. After recording the readings I shut off the car and bled off my gauges. The high side hose was filled with a yellow liquid substance that I assume to be oil. Is this normal? Also, I would appreciate any insights on my readings. I realize AC systems are best left to the professionals, but it's an old car and I like learning new things.