yea i agree. with stock software mine only boosted to near the end of the yellow. i have nordic stg 3 now and depending on temperature it will boost a little bit into the red at most. the middle of yellow seems a bit low for stg 3, you should pobably get a boost gauge if you can for a more accurate reading.
heres some things to check:
i would first try resetting the ecu and readapt it
check all vacuum lines and charge lines including the ic
check your sparkplugs
check boost control valve
check wastegate actuator
check bypass valve