These videos might be worth your time, might want to check into getting a Synapse Synchronic BOV. Sounds like your blow off valve is having mad compressor surge causing your turbo to spin in the opposite direction.
http://videos.streetfire.net/search/...3f0150f005.htm
http://videos.streetfire.net/search/...620138267b.htm
No diaphrags, Pull type blow off valve, Poppet valve for max flow at intial opening, Boost pressure in intercooler pipes keeps it closed.