engine running lean – kia forte 2.0 2010

hi
i recently bought a kia forte 2010 2.0. 30 minutes after driving off from the seller, the check engine light came on.
code p2191: lean at higher load bank 1.
i replaced the upper o2 sensor, the map sensor and the pcv valve.
i took a look at the sparkplugs, and they were all a little white.
i have also tried looking for vacuum leaks, by holding a hand to the throttle body, which killed the engine – therefore i suspect no vacuum leaks?
the engine does not misfire, it starts right up and runs smoothly – the only signs of it running lean is the lack of power and the cel.

if i get directly on to the highway within 10 miles, the cel will not come on.
if i drive around town for 10-15 miles it comes on, when the engine gets warm.
if it is already warm and i drive around town the cel will not come on.

maybe you can help determine what the cause could be?

best regards the frustrated amateur mechanic

brand: kia
model: forte
year: 2010
engine: 2.0