I did some thinking on the basic results from my rerouting of the WGA (see my "poor mans boost controller" thread). Note that my guage is in bar, not psi, so my psi numbers here are ball park.
What we are seeing in non-stage 1 stock cars when the boost drops to around 5psi is just the WGA doing it's job. duh, it's a 4-5psi waste gate. The 12psi or so we see it run up to in stock is the PCM letting the boost run up before it opens the WGA solenoid - what we have in the PT is an EBC at the #2 solenoid, and it's tuned for midrange punch (like a dual stage boost, but stepping down instead of up).
It would seem the simple way to override the PCM's RPM/Boost/etc maps for controlling the WGA is to just cap of the line from the #2 solenoid to the WGA, and just use another pressure source to feed your MBC/WGA. This would bypass the #2 solenoid and the PCM's control altogether, and let you hold whatever boost you wanted to redline. In my case, w/o a MBC all I had was the base 4-5psi of the WGA
I'll be using a larger bleed valve and see what happens
If you prefer to have that boost drop off at higher rpms, but want to raise it to a higher point (say, 12psi) then putting the MBC between the solenoid and the WGA would seem to let you adjust this part of the picture (as others have noticed).. it would seem that setting an MBC here at the same point as the factory peak would remove the boost drop as well. I'm not really sure yet what would theoreticaly happen if you were to crank up the boost point here to higher then stock..
Placing an MBC in front of #2 solenoid would seem to let you run up higher then stock boost, but then the boost drop would still be managed by the pcm. Place an MBC at both points (maybe just a bleed after the solenoid), and I would think you could get full controll - give yourself a 18 peak before the solenoid, and drop to 14 after the solenoid, etc.. pick up some solenoids and rpm switches from an NOS supplier, and you could have all sorts of fun
but then an EBC would be easier!