'83 Vanagon / inverter question

[seann]

I use an '83 Westfalia for some of my decal installation work as well as a camper, yesyerday I had to use my 700 watt inverter to use a heat gun for 5 minutes to remove an old decal. The inverter clips directly to the main battery with 2 outlets for AC. I left the van running while using the heatgun, packed up, and left the jobsite. The van was running VERY rough from the moment I pulled away, as if it was running on only 3 cylinders. Just wondering if there could be any connection re inverter.
Thanks