lukewarm heat in car

Okay numerous repairs radiator, waterpump thermostat. All done by me. Recently pulled the heatercore to flush and confirm its not clogged (when radiator got hole tried bars leak). Temp gauge shows half way when running . Plenty of coolant and I put van on ramps and ran with rad cap off to let air out. Car got moderately hot on ramps especially if I revved it a bit. However when driving it only gets lukewarm. Car does not overheating. Did the calibrated procedure (press rear wiped and wash ) which didn't seem to change anything. What have I missed or screwed up