What is a code u1900? My truck has seemed hard to start since I bought it. Also, after the truck's electronic throttle control light lit up yesterday, the truck is running different. The turbo isn't as loud, and seems to run through the rpm band faster. And the dash is showing some crazy fuel milage, like between 23 to 29 mpg ( know its not acurate by no means), before it showed 16 to 17 mpg (I know, it's not acurate, I get 14)

No smoke, no obvious temperature issues. still makes boost. I dont know this motor nearly as well as my old 5.4 triton.

Any advise on what to look for?

 

Could be this:

Various Electronic and Driveability Symptoms and Codes:
2005 F-Super Duty trucks built before 5-11-05 may exhibit various electronic-related symptoms due to loose/miss-installed fuses in the engine compartment fuse box. These symptoms may be intermittent. The fuses should be inspected to verify they are installed into the terminals in the fuse box and not along side the terminals.
Fuses--Symptoms
#9, 20 amp: Trailer turn signals inoperative
#10, 10 amp: Check Engine Light; Codes P1633, P0446
#11, 10 amp: Speedo bounce, ABS light, Cruise control inop; Codes U1900, U2023, P0500-P0503
#12, 2 amp: Cruise control inop, TBC Fault displayed, chime; Code C2803
#13, 15 amp: Day time running lamps inop
#15, 15 amp: Crank/no start, bucking, stall; Codes P2614, P2617, P1378
#17, 10 amp: A/C inop or not cooling
#18, 10 amp: Crank/no start, bucking, stall; P2614, P2617, P1378, P0611
#20, 10 amp: Trailer back up lamp inop
TSB 05-11-14

Check fuse #12.