Diesel Bombers - 2001 24v issues

I am new to forums and dont really know where to put this. Sorry if I screwed up!!!

I have a 2001 CTD with a couple of issues that I have not been able to pinpoint.
1. Miss at idle. Hot, cold, doesn't matter. Tach bounces and you can feel the truck missing. Has done it ever since I owned the truck. I have a new VP44 with less than 5k on it from Gillette Diesel and it didn't clear up the problem. It had the same issue with the old VP as well
2. My fuel pressure holds at 20 psi at idle, drops to 14-15 on the highway @ WOT doesn't seem to be an issue but if i turn the truck off and go inside for 20 minutes and go back to the truck, my fp gauge reads 0 psi with the truck off. Should it read 0 before cranking? I figure it should still have some residual pressure from the last time it was running.
3. When revving the truck and letting the rpm come down on their own, the motor "surges" when it comes back down to 750 rpm. It does it when you're driving as well. Doesn't seem to affect driving but I would like to know what is causing it.

It has been tuned with a super chips 3705 on perf settings. I have returned truck to stock and has not cleared up idle issues.

Thank you in advance for any insight you can provide!!