Newbie here guys but I have been searching threads for my problem but haven't found my exact problem. Here's my history, I have an 06 LBZ 3500 with a PPE tuner on setting 1 for last 3 years. Truck has 243k miles, all original. Early last fall I replaced the fuel filter head from DMAXSTORE after researching why truck wouldn't start, would have to prime fuel filter and would then start. Lately while cruising at highway speed while towing heavy load, over 30k lbs, engine light comes on, loses power, won't rev over 1800rpms, it still keeps going just has very little acceleration or power. If I have to stop it will shift through gears just won't go over 1800rpms. I've found that the fuel filter has lost its prime and if I pump it back up and bleed it, it will continue, initially it was 20-30 miles before doing it again now its not lasting long at all. Once I unload its fine. During this time the fuel mileage also sucks. The only consistent code is P087 for fuel rail pressure to low. Could it be a faulty fuel filter head again or something else? Thanks for any help.