that black pipe is your recirculation pipe, goes back into the air intake just before the turbo. You can just block that off. With the stalling you should not have a problem if the spring is set tight enough. If its too loose the piston will not close before the throttle and you will stall. If you can see the piston from the outside of the BOV, rip the throttle so the BOV goes off and watch the piston on it. The piston should be completely closed about a second before idle.
Do you have an exhaust? if so you will prolly get backfire not matter who fits it. From what i have heard/been told the skylines run a bit rich from the factory causing backfire and an exhaust will act as a bit of a microphone for that I had a BOV before exhaust and did not get b/fire, put an exhaust on and got it. Sorry bout the length.
Steve