I have a 93 J30t with 184K miles. It runs smoothly and gets good gas mileage. However, when I have been running w/o the lights on for a while and go to flash the headlights, it makes the engine hiccup. Its a distinct occurrence similar to several sparkplugs mis-firing. After the hiccup, I can flash the lights without a hiccup. I put a voltmeter on the battery and the alternator output looks good. When I flash the headlamps the first time, the voltage goes down to 12v for just a split-second then returns to normal to the 13-14v range.

you may need a new battery with better amperage rating or you might need a newer alternator to supply the power drop. r u talking about using your hi beams?