wouldn't mind betting that a lot of people don't get a decent boost hold with the AVCR because it's not setup right. when I got my car (fitted with avcr) it was set to run 1.35bar, it only ever peaked to about 1.2bar and held circa 1.1bar.
I wired it up for self learn instead of injector duty cycle, added a bit to the in gear start duties where applicable and it makes desired boost now and goes much better.
In my experience of using quite a few boost controllers (HKS EVC's, Blitz s & R, Greddy, avcr) the HKS EVC's are the worst.