2003 - 3500, Auto tranny. Fass Fuel system is only Mod.

When trying to hold about 65Mph, I seem to be losing fuel pressure, or maybe boost? or something else?
Hard to really know without gauges...

RPM's go down, speed goes down, yet my foot is not moving in or out on the pedal... she just slows right down.
If I lift off the gas pedal a bit it kicks back in and starts to pull again.

Really noticeable on hills, and/or when towing, but same issue without weight.

With cruise control on, hills are a breeze and I can maintain 70MPH up hills with my light loads.
Without cruise, I can not maintain highway speeds unless I am constantly on and off the gas pedal..

So the computer must be adjusting or doing something.

Ideas?

 

Without a fuel pressure gauge, its very difficult to tell. Have you swapped out your fuel filters, drained the water separator? What is your air cleaner like? Hate to point out the obvious, but I like to check the quick and easy things first.

Check your boost boots too, make sure there is no leak anywhere...

 

sounds like apps