Just to add, my Gems was on a classic (my98) so i cant comment on running on a newage, as the newer ecu has more functions than the one i had.
But even then,
Cold start was a nightmare, hot start was a nightmare. Idle would vary, boost would sometimes not hit target, and then othertimes go way over target...
Yes, you get lots of pops/bangs/flames...But not worth paying the extra money, and having the extra hassle just for that.
Although, mine was only ever mapped by one mapper.
As for Anti-lag, it worked extremely well on my car, never once had an issue when braking.