I made my own mbc and it hit 15 psi and dropped gradually to 12 by redline.
http://www.geocities.com/chmwatson/FAQs/mbc.html I threw on my ebc with the stock t25 and it would still drop down by redline. The t25 turbo has problems holding boost levels that high, unless an avcr is really that legit.
Honestly, besides the ability to change boost on the fly, I'd prefer the $12 hardware store boost controller over my greddy profec type-s.