Occasional Miss

1996 ram 1500 with a 5.9. At idle, I get a bit of a miss. Fine at speeds. I've done plugs (3923's), cables, rotor, cap, all throttle body and sensor stuff. No codes present. I have times when it runs smoothly and it seems to have more pep, but I can't nail down just why. Here's another clue from yesterday: I was giving a jump to someone and in order to give it a boost, I revved the engine a bit. It missed like crazy! Once I disconnected the jumpers, it was back to "normal". So, an ideas out there? (Thanks!)

I'd check the voltage on the battery, as well as the battery cables for corrosion.

I hooked up my schumacker charger/tester to it and it gives me a check light. Alternator percentage flashes between 0 and 12. Something is definately wrong! I will keep you posted.