I'm using an adjustable vacuum switch on my water injection and I pretty sure it (the switch) is not functioning properly. I have adjusted it in increments and the results are not monumental in difference. I have an led which lets me know when it is activated. I know that either the switch is defective or I am not utilizing a good vacuum source. I tapped into the vacuum line on the back side/left of the motor (looking from the front).
If you have a certain value that you're looking for (i.e. your setup requires a tap to a line with vacuum of more than 10hg or something,) you could always buy a cheap vacuum gauge from Walmart, etc, and check each line until you find one which suits your needs.
I'm not familiar at all with your setup, so that's just a very basic recommendation.
Try tapping the vacuum line going to the fuel pressure sensor. I know that is a good source since that is the source used for the bypass on my supercharger. If that one doesn't work, you know it is the switch.
It's still there. I think it's a bad switch because the line I'm tapped into originates at the same point as the one for the fuel pressure sensor. I appreciate the help with this one. Because we are still feeling the effects of Katrina down here, it's tough getting to parts houses and/or wal mart or wherever. All those places are either destroyed or work limited hours...still! I can order another switch for a lot less pain than driving around searching. Thanks again to ya'll for responding.