I think that a piggy back tunes ability to log certain parameters and read codes etc is far more valuable than the headline power increase.
My turbos appear to be crapping out. Looking at the logs and discussing with Terry allowed me to diagnose this more readily.
Car: 2010 Jaguar XFR (Cat-back exhaust)
Gone but not forgotten: Highly Modified E90 335i LCI M Sport Manual (circa 480BHP/500lb ft)