Normally get underboost fault codes if the DV pops. If that was last done 6 years ago, it might not hurt to stick another one in, or better still, a GFB DV+.
Also do all the usual PCV checks and look for signs of oil sweats around the intercooler pipe connections. A common thing there is the metal boost pipe ovalises due to the extreme amount of engine movement down there. If that happens, you will need a new pipe as well as a new O ring.
It's also a good idea to log the actual vs requested boost pressure with the scan tool, and also actual vs requested fuel pressure. Boost reductions aren't just caused by leaks, the engine ECU will cut the boost if other problems exist to protect the engine.
It's always best to be armed with as much info as possible before approaching the tuner for advice because 9 times in 10, they always blame the hardware.....and to be fair, it usually is
