Here is what I woudl suggest but I defer to those with more experince:
I see you have the Air dog 150 and also a Walbro.
The air dog 150 is good at removing air although IIRC
the 100 model actually does a better job of that from what I understand but a smaller pump. Regardless you have the air removal. The issue is the air dogs actually are quite sub par at removing water from the fuel. It does a decent job at removing solids but the filters it uses at that stated max flow rates are way over taxed. The later is likely not an issue at your power levels. You also should always have a filter after your last pump before your injectors. I will post info on the air dog and other filters at the bottom
What I think the goal given what you already have is to design the system so that you get the most from everything and protect those injectors as that is a $2500 investment to replace.
Most fuel water separators are vaccum or suction side filters and not meant to deal with head pressure. Given this:
I would put a water fuel sep between the tank and your air dog. Then the final fuel filters between the walbro and the heads. Delete the fuel bowl as you are having issue with it any ways and they can tend to be a PITA and take up needless from. Get a ITP kit of DIY
. For ease of changing out the filters and preventing drain back you can install a check valve right after each of the two filters you add. ADD a Aeromotive or Fuelab regulator. You can run a tube from to the map
to adj fuel PSI
based on boost 45 min 65 max. Then run into the return and you have a complete Reg Return as well.
Unless you add a good amount of power which your PMRs
likely prevent you can likely get way without upgrading the fuel line size as you already said you do not want to be cutting and what not.
About the Air Dogs 100 and 150 I pulled up the filters used specs from a couple of sites:
The FS19768 which is the fuel water sep filter on the airdog models is not rated to remove any emulsified water and its only rated at 50% for free water. It also only has a solids filtering abilty of 140 microns. The thing that got me was the water separation performance. Compare that to the commonly use BF1212 (fuel water sep) 20 microns absolute, average efficiency of 86.34%, Water stripping: 97-99% free water, 92-95% emulsified water. And it has a dirt holding capacity of 35.9 grams, 579.0 sq in of filtration media, and a flow rating of 210gph that to of either of the AirDog.
the other ting I have not figured out is the ther filter the Air Do units use as their second fine filter is the FF5613. They state it as a 3 micron filter, but its really a 5 micron filter. absolute at 5 microns, 94% at 2 microns. With a flow rating of 59.97 GPH. If the Air dogs really do flow 100 and 150 GPH respectively they are pushing these filters well past their stated flow capacities.
Based on this I do not believe the Air Dogs meet the water remove minimum rating for diesel motors. I certainly would not rely on it.
For the fuel / water separator I would run a BF 1212 or FS 1212. I prefer to run Baldwin filters as they have a thicker casing than the other filter manf filters. They also have very good specs and can usually be found at most truck stops if on the road.
For the fuel filter post pump before the heads I would add a filter such as the BF7633, FS5320, CAT1R0750, or Donaldson P5513132. Also the Wix/NAPA equivalents. Pick up two 1-14 filter bases. Wix/NAPA has some low cost choices such as the 24770/4770.