had another brainstorm come over me a couple of months ago ...
dual wastegates (ie internal/external).
it'll basically look like this:
WHY you ask?
well... this way you can have your cake and eat it too:
1) retain control over relatively low boost situations by springing your IWG only hard enough to hold the max boost you desire. right now my iwg spring is around 12psi and it'll hold >27psi (tested!
2) the EWG only opens up when the MBC does. the MBC controls max boost only. put a spring in it sized a few psi less than the minimum boost you want to VTA. in my case i'd put a 1-1.5 bar spring in.
3) since the 3-port solenoid is controlled by some electronic means, you can map desired boost to TPS and RPM. basically if you want max boost and EWG operation you send 100% duty to the 3-port. anything less will mean the IWG is open and limiting boost to some lower value. no issues with PTFB and boost control is retained at lower levels due to the relatively light spring in the IWG.
4) car is only wicked noisy when the EWG is open. when it's not, all turboback exhaust is in normal operation... ie, cats, mufflers, etc. who cares if it is restrictive and quiet, since:
5) when the EWG opens, you get the big VE benefit of a VTA dump. and it'll be noisy too!
the astute may notice that, on my car, this basically entails adding the EWG up pipe and actuator, removing a tee, and rerouting one pneumatic boost control hose to the new EWG.