The truck runs and starts fine but I have a fuel drip around the fuel filter cannister. I don't think it is around the cap, tried wiping it off but hard to see where it is coming from.
Any suggestions on how to locate?

 

Big leak? Small leak? Might be a cracked filter canister lid. You can try to wipe everything down then start the truck and at an idle, move a rolled up newspaper in there to see if anything is spraying on it.

#4 injector line is prone to cracking. Don't get your hand/finger anywhere near the High Pressure lines that might be leaking. Newspaper can be replaced, body parts not so much.

 

If the line was cracked would it run rough? I put a metal cap on it years ago so the cap is not cracked. The leak comes and goes, from a drip every 10 seconds or so to nothing. Warmed it up this morning, idled 15 minutes and had a big wet spot, idled same time this afternoon and nothing. On the front of the canister, about 1" down there is a lip, looking aver the tire I could see it dripping off the lip on the back, engine side, then it quit.

 

Check for a cracked / broken water drain valve. The yellow lever on the stock filter canister. If you had a fair amount of water in it when temps plummeted i've seen the valve crack.
Not the lever

 

Presume this only started after you changed the filter? Any chance that you could have mistakenly installed two gaskets (O rings)?

 

It was leaking where the heat element goes in.