Hello fellow diesel fanatics

I recently did a minor overhaul on the r4 system in my w116: accII upgrade kit from unwired tools, new receiver/dryer, expansion valve, flushed out system etc. There are no vacuum leaks and the system holds pressure just fine with no refrigerant leaks. Pressures are approximately 25 psi on low and 200 psi on high side at 2000 rpm.

The issue: Vents blow cold when traveling under 40 mph but at highway speeds, becomes warm. The air coming from the center flap feels almost like dehumidified air. Very strange indeed. The problem appears to be very counter-intuitive.

Anyone experience anything like this?

Thanks in advance, I'm sweatin my balls off on the highway.