On TBI trucks, the base timing is usually set at 0. With you adding the extra load on the electrical system, you will have to compensate in the tune. Here are some parameters in $0D yon can try....

You need to connect the ac clutch positive wire to pin E12 on the PCM. The PCM needs to know when the AC clutch is engaged. It also has rpm tables in the tune to compensate for the AC engagement. See...