I have put on 5th injectors with pressurized switches attached to them, so that they come on after a certain amount of boost. I have switches that I have sold before, but only have 1 now. They are easy to set and also I put on a light with them, just so you know that they are in working order. You can set these from like .5 to 20 psi. they are good and reliable. I might use a 5th and 6th injector setup in the future just to try it.