I've never had this problem with these motors and was wondering if anyone could point me in the right direction.

yesterday sucked bad i was up in moab on hells revenge and it was running a little rich when i got there and it got a little worse as i went blowing black exhaust and missing bad. I'd have to rev it to clear it out so i could make it up the steep parts without stalling! Any ideas? Thanks

1987 4Runner SR5,SAS,6 inches of lift,35in BFG's,Welded Front,Detroit E-Z locker V-6 Rear, 5.29's