1993 Isuzu pick up 2.3 L. When driving about 80 on the interstate with my AC on full blast I lose RPMs unless I turn my AC off. What can be causing this

What is your question?

93 Isuzu pickup 2.3 L. While driving on the interstate and turning my AC on, my truck start slowing down and surging. I have new belts, need help diagnosing what’s wrong.

What makes this problem better or worse?

Happens when I turn on my AC

How long has your 1993 Isuzu Pickup had this problem?

Two weeks