1. Dodges don't have glow plugs( they use an air heater in the intake)
2. turbo spool is based on how much exhaust gas you can move out based on air used coming in. so if you have a stock air box don't waste your money building a huge open exhaust.
3. if you have a nice open air box like a K & N or better system then you need to expand the exhaust. 4" or 5" pipe is best with a low restriction muffler. do not run without any muffler. it needs minor back pressure to keep the system stable.
4. if you can't get fuel in, the engine has nothing to use to make power. Like a couple people have said does it have a fuel problem now? if so fix it first before you waste money in other areas.
5. Bio crud in fuel . diesel is as close to a an organic compound as fuel gets. algae does grow in it. its a black nasty algae to. if you have it the system act like it can't make power by causing the fuel pump to cavitate. it will ruin your engine. treat the fuel regularly with a good bio guard system cleaner and change filter a few days after every service. that way when it does kill stuff the filters pick it up and you remove it before it goes any further.