Lots of people will give different replies to this, but here is one suggestion I used and worked. I had a ramcharger hood on my car, and hooked my canister directly through my switch off the intake manifold. I never used a spring and the switch in the car did not have the solenoid hooked up either. The trap door sprung open and stayed open the entire time I was cruising with no issue. If I let the switch in the "open" position, it would take several hours to finally close. If I switched to the "close" position, it would fall as soon as I shut my rig down. I had to experiment with the setup a little at first, because one way I had it hooked up, the door would never open, one way I had it hooked up every time you touched the loud pedal, the trap door would momentarily fall flat then spring back. The final way was what I wanted, full open with no issues while running.
This was with a car that had a stout comp xtreme energy cam and no vacuum cannister (as in additional cannister)
I drove the car in the rain many times with the trap door open, never a real issue in the way the car ran or detail department at all, and i was meticulous about the engine and bay appearance.
