2000 V70 XC runs rough after 5 mins.

[sorenmail]

Anybody have any solutions to a car that starts and runs fine but then goes rough after 5 mins - rough idle, poor throttle response, what seems like "limp home mode" w/o the flashing arrow - and then starts fine an hour later and experiences the same symptoms after 5 minutes? Threw a P0121 (TPS/Pedal Position Sensor A CKT Range/Perf) and a P1238 (Manuf Control Fuel Air Metering) code.

Background
Wagon has 183k mi on it, 30k mi on XeModeX ETM with ETS light on the last 20k mi, 23k mi on rebuilt trans. Have never replaced MAF or O2 sensors. Alternator putting out 13.9 volts. (XeModeX rep told me 2 yrs ago that the ETM needs 14.1 volts to work properly and the low voltage is why the light was on. Car ran fine so I didn't replace alternator)

Thanks in advance. Would love to get back into the comfort of my XC and out of my Sienna!