OK, I have a 12a streetport that I fitted with a S4 turbo with a 12a exhaust flange and blowthrough box I cut and had wielded by a friend for my weber sidedraft.

OK, with that, with stock boost(with a ported wastegate) was about 4-5psi boost, and some lag. I'm running 2-1/2piping, with a turbo muffler mid way back and rice cannon out back. Sounds deep and nice, flows pretty good. Power was good for a turbo 12a, even at that level.

However I knew I'd be getting a boost controler sooner or later, so I decided to get a $39 Rick Gillis manual boost controler(because it was cheap), and even with it set at 5psi, the lag is much less, and torquyness is way up with boost coming on much harder and quicker then before. I wish I had installed this sooner!

Just thought I'd share this, because it sure utilizes the turbo better now.

 

That's nice of you to share... MBC's are a super value in my opinion. But... electronic boost boost controllers have significant advantages -significantly less wastegate creep which translates to even less lag.