Source Auto used to sell a mechanical kit i think?
I bought a cheap Ebay special BOV that i was gonna put together on my truck but never got around to it. I was gonna follow a thread on another forum and try it out.
Mount the BOV on your IC pipe, plumb a copper drive pressure line to the top port and run a very light spring in the BOV. You might have to mess with a few different springs to get it to blow off properly.
The guy i was copying had great results after tinkering with different springs