Misfire,boost problems,reverse light problem

[ffmozer]

Okay I have a 2000 F-350 7.3 with around 127k miles on it. I work at a dealership so i have access to a shop and tools. my truck started to misfire about 3 months ago and it wasnt all the time it was intermittent usually on light acceleration or when i maintain speed after accelerating. I pulled codes and it said #8 injector so I replaced it along with the gasket and wiring harness under the valve cover. About a week later the misfire comes back and has been doing it ever since sometimes its bad and other times it barely happens. I pulled codes about a week ago and i had a pcm failure so I replaced that and took out my banks six gun tuner. Before I pulled it out the tuner would say boost error and the turbo would boost while accelerating and then just drop and stop boosting. after I replaced the pcm and took out the banks the truck still misfires and shows a #8 injector code. I also cant get the truck to really get over 5lbs of boost and it runs very slow. No one at the shop can really figure out what is going on because it seems to be an electrical issue and theres no code that says just replace this and your fine it could be a number of things. But as of right now i have a new pcm, slightly new injector in #8 new wiring harness and gasket. Also every time i throw the truck in reverse it blows the fuse for the reverse lights and my vaccum pump is on that same fuse. I replaces the digital transimssion range switch and that didnt do anything. not really sure what to do with that im not too good with electrical things. Any help would be appreciated this issue has been going on for to long and it gets annoying because this is my daily driver.
thanks,
-Chris