Hello my 88 Jimmy 4X4 4

Hello my 88 jimmy 4x4 4.3L just starting to buck and seems to lose power as I reach 45 -50 mph I slow down start to pick up then does the same friend at my local shop hooked it up came up with code 42 timing /spark issue could this be the ICM starting to go bad? Hope you can help! ED
not what I need a my truck acting up good old Sandy wrecked most of what I have already thank god for good friends!