Chevrolet Repair: rough idle 03 8.1L 2500hd 21k miles, check fuel, fifth wheel

Question
It is really bad at a stop light and I can feel it fall on its face a little in higher speeds.  I replaced plugs about 2 weeks ago but after this last weekends trip towing my fifth wheel it seems worse.  It had a minor stumble before plug replacement and plugs looked good.  Thanks for any info,looking to fix myself if I can.  -T

Answer
Hi Tony...I always start at the basics. check fuel filter, fuel pressure. check for corrosion in any wiring connection. if that isn't the problem. check the codes. if you have a random misfire it could be a bad coil or wire. check and clean idle air control. do you have a service engine light on. a scan tool will help track the problem as well. Pull one plug wire at a time and see if each cyl stumbles the one that is not noticable is a bad one...hope this helps