Mine does not have the grey one (A/C). I am guessing the other three are: One is for the secondary air (pair valve) One is for the fuel pressure egulator One is for the egr and egr modulator just curious of what color is which.
my 94 only has three, does not have the egr one, it's done by a temp. switch on the intake, the gray one is for the AC idle up, the brown one is for the pair valve and the blue/green one is for the fuel pres. reg., just did the delete of the pair and egr, the only one I kept was the fuel pres. reg. and you can do away with that one and just use one vacuum source to reg., but I decided to keep it............