Where does one plumb the air filter monitor doo-dad?
Somewhere downstream of the air filter element.
I suppose you could cut a hole in the top center next to the fixing screw of an AF big enough for the rubber grommet. I'd be hesitant to do that on an original oil bath though. The thing about these monitors is that they record the peak restriction at full throttle and high RPM. Unless you live i a dusty area it's probably overkill. Just change the paper element at regular intervals or blow it out with an air hose when it's dirty. You should be able to see light through it when you're done. On an oil bath see how much dirt is in the bottom. They will hold a lot of dirt before the metal gauze needs washing. I do mine every spring and they're rarely dirty enough to bother but I do it anyway cause it costs about a pint of oil each. And it can be cheap oil too.
On diesel trucks it was usually in the pipe between the turbo intake and the external AF mounted on the side of the cab. Later, KW and Pete moved the AF under the hood and that raised the noise level in the cab. They included a note in the operator book saying not to worry about the "chuffing" sound at low RPM. Peak torque by then was down about 1100 RPM.
I'm thinking about a way to get the two air filters on my rig out from under the hood so it still looks good. Haven't come up with an idea yet. At full throttle they are noisy. The car ones had big silencers on them. If I found 2 car ones I'd install them. providing there's enough room between them.
