89 Ranger runs rough (only with Alt Hooked UP)

1989 Ranger , 2.3L 4cyl 2wd

Timing Belt snapped ,Replaced Belt (Valvle Timing Correct)
Vehicle Runs VERY rough ,loses power , won't idle without help from Thtottle.

As soon as i unplug the Alternator it runs perfectly.

Any ideas?

Thanks

Replace the alternator and see if the problem is still there.