I just purchased a 2003 E 150 with a 4.2L v6, with 94000 miles, it is replacing a badly rusted but mechanically sound 1998 e 150 with the same motor 170,000

My problem is after driving on the highway the thing started throwing codes 0305,0316. changed plugs, GOING to change wires and coil packs.

cleared codes
yesterday threw 0181 fuel temp sensor, EFT sensor is located where??

cleared codes
and today nothing except voltage meter kept fluctuating from I'd say 13 to 16 volts while at cruise speeds.fine at idle.

any ideas , still have the 98 to swap parts.
will have coil packs and wires on tonight.

ALSO did change out alternator as it was only 1 month old from 1998 145 amp, looked the same.