I just finished putting on a NEW head (no milling done) with o-rings, studs and a .020 Cummins Gasket. I also installed a set of DDP4s, and reset the timing to 18* as per recomendation from you guys.

Now, the truck has a rough starting issue. I thought it was the timing, so I rechecked it with my Snap-On kit and it is right at 6.0mm lift (215hp pump).

I also thought it was an air leak, (whits smoke, stumbling when started) but I just re-did everything over the summer, new supply and return lines, lift pump, rebuilt heater and pre filter new orings and all, new overflow valve. I pressurized the fuel system yesterday with #8 of shop air and a modded gas cap. I let it pressurize and sit with the air running for about an hour. NO leaks that I could find.
After I was done, I had installed a Holley Blue fuel pump on the frame rail. I thought this would help in the hard starts and I also am going to need it for the twins project.

Now, today it was about 25* out and when I was leaving the hospital (truck sat there since 3:00pm Sat. afternoon about 30 hours) I went to start it, cycled the grid heaters and fuel pump twice, and it barely started (had to crank it twice for about 5-8 sec. each time) and when it finally fired it was like an old piece of diesl machinery, it chugged and popped and blew white smoke all over for maybe 10-15 sec.
The good news is that the timing must be right on because it doesnt stumble anymore when I take off with it.

Is this because of the new head (no milling done) and the .020 head gasket lowering compression?

Also, I have been reading up on the AFC fine tuning. Does the AFC have anything to do with starting since it does control pre-boost fuel? I havent had the chance to adjust it this summer because I was so lazy.
It is still set from the previous owner, loose star wheel and AFC screw tightened all the way up, so it pours the black smoke.
Yes, I will be adjusting it, as soon as I can.

 

Your 20 over marine gasket is causing the hard starting, especially since it is a brand new head that has not been machined. My head had 4-5 thousandth taken off of it so i opted for the 10 over gasket to stay away from the hard starting. Especially since I live in Northern Idaho.