I was going up to Onyx summit near Big Bear CA last Sunday morning around 7:20am, on the way to a bike race. It was a little below freezing and as I went through the 8000 foot level my car lurched a couple of times and then unloaded down to 10 psi. I was at half throttle accelleration when the engine got to about 3100 rpm and the boost to about 17 psi it just unloaded. I tried this several times and it repeated. Once I got the car below 7000 feet the problem disappeared. I have the stock BOV with a Buschur MBC set at 20 psi. I was running my 93 octane rocket fuel at the time. I have never had an indication of a problem with this setup before and my car usually hits 20psi by 3200 rpm. I think that the BOV spring was seeing the 4 psi lower pressure outside because of the altitude and couldn't hold the normal 20 psi. I'll bet my BOV would unload at about 24psi at sea lever. What do you guys think.