As stock BOV's (or BPV, CBV) go, the DSM 1g BOV is pretty stout. They will routinely hold between 18-21 psi unmodified. Once you get beyond that threshold, it is possible to get the valve to hold even more pressure by "crushing" it in a vice. This does allow you to hold more boost, but the preload on the spring can cause it to incompletely release. As well, travel of the valve is reduced, and if you're trying to run a lot of boost, it may not vent enough air as a result.
The solution to this problem was first deduced by Gus Mahon (RIP). By removing boost pressure from under the valve under high boost (in this case, >15psi) conditions, it keeps the valve solidly shut until the manifold sees vacuum. Gus' original solution required you to run a switch to manually change between "high boost" and non modes. Dejon Tool has found a solenoid that will automatically switch, resulting in being able to hold high boost easily, and maintaining good part-throttle BOV release characteristics.
Not trusting myself to modify the valve myself, I sent a 1g BOV to Dejon for modification. It came back with the fittings already connected, as you can see in fig1.
The lines come already attached, as you can see. The only unexplained line is a hose ending with a brass fitting and a small label that says "to boost source". This line is meant to be plumbed into a pre-throttle-body boost source, i.e. somewhere in your intercooler piping.
Don't forget to Teflon tape, or otherwise seal, the plastic fittings where they screw into the solenoid. As well, the one port that is unoccupied by a line should remain open, do not cap it with an NPT cap or anything like that.
So, you have to somehow make an allowance for this new fitting. I drilled a hole in my DSS upper intercooler pipe on the underside, so it would be somewhat stealthy, and threaded the hole. You won't have much metal to work with in your intercooler pipe, so be very careful when tapping it. I used a few small dabs of gasket maker on the back of fitting to ensure a good seal.
The last question is where to install the solenoid. There was a nice clean spot under my fusebox, so I cleaned it up with some alcohol, and mounted the solenoid there, as pictured. trim lines to fit - the shorter, the better.
Another good mod, fortunately! This modification was essentially transparent, as it should be. If I lift suddenly at high boost pressures (>16psi), the BOV makes a much sharper, louder TSCHOO than it used to, but that's about all I can detect.
So far I haven't experienced any strange part-throttle behavior either, which some folks have mentioned getting with this mod. Perhaps there is something they are doing different. I pressure-tested my intake up to 26psi with no leak from the BOV (previously it cracked at 18psi), so it looks like the mod has done its job. For $60, with no apparent downsides, I definitely prefer that to spending $250 on an aftermarket BPV!
Next Stop: Big turbo!