286000 MILES-- HAVE HAD CODES UP (FUEL SENSOR) SEVERAL TIMES THRU THE SUMMER--had it in to dodge dealer numerous times with no solution---had check engine light cleared before we left for a trip from MI TO WASHINGTON STATE-----RAN GOOD ALL THE WAY THERE WITH OVERHEAD SAYING 16-18 MPG.
ON WAY BACK ENGINE LIGHT CAME ON AGAIN--SOME BLACK EXHAUST SMOKE--NO CODES--DROPPED TO 13 MPG OVERHEAD---NEXT MORNING ENGINE LIGHT OFF AND FUEL MPG UP TO 16-18 AGAIN
REPLACED ALL INJECTORS THIS SUMMER----HAD ALL THE PLUMING TO THRU AND FROM TURBO CHECKED ALL CHECKED WELL---NEW AIR FILTER

 

Just spitballin but could it be your lift pump starting to pack it in? Does it feel like it is losing power when your mileage drops?

 

the only difference in performance is a little bit rough idling

 

As my stock lift pumps died mileage would decrease, power would be down - subtle at first and worse as it progressed but very noticable when pulling. The CP3 has to suck fuel when the lift pump dosnt supply enough and eventually more problems develop. My CEL only came on at the very death of the pumps but I have an 03 and it may be different than your 06.

Hand calculate your mileage rather than relying on the lie-o-meter to be sure on the mielage front, however given the codes and smoke and if they have gone through the fuel system an intermittent lift pump issue might still be the cause.

With your mileage are you still running on the original stock pump?

What codes are you throwing?

 

has never lost power dodge dealer has said they think might be fuel rail sensor ( 700.00) --but hey won"t garentee replcing it wil take care of problem.
Lot of 700.00 items on the truck----don't want to chase the problem down by installing 700.00 pars till they find problem
Same fuel pump CP3----never any issues with it

 

Cheaper to get the parts from places like Genos once you figure it out.
I was thinking more your in tank lift pump rather than the CP3 but it would be good to know the codes it is showing before chasing parts. Could be a number of sensors or the FCA and things like that. weak battery, loose conection at the sensor.... The service manual will give some guidance based on the codes.