Hot Hatch LIMPS HOME? (VW GTI Throttle Malfunction)

This 2007 VW GTI 6-speed manual actually drove to the shop from 3 hours away! Owner says that most days it's NOT HAPPY, going into REDUCED POWER mode intermittently. Lots of codes set, including TPS circuit codes. However, on the test drive it runs BEAUTIFULLY!! How do we approach a problem that we can't recreate? MEGA DEAL... THINKTOOL PROS: *****TOTAL $270 OFF!!*** USE CODE: BIGGA4NX https://www.amazon.com/dp/B08SWH2KP4?... TS100 SOLDERING IRON: https://www.amazon.com/dp/B07SQDZ9SV?... Enjoy! Ivan