I know this is an older thread but I've been reading more about 15B's and came back to it.
I'm still not totally sure how all of the throttle linkages work on the different iterations of the 15B. In that first video I posted you can clearly see the guy revving the engine up and down using something that goes down into the intake tract. I don't see anything else connected to that, either. You can also clearly see the PCV hose goes into the intake right there too, so they must be using some sort of vacuum there to pull out crankcase pressure. Although that was an N/A 15B so perfectly feasible. But it just adds support to the idea that there might be a vacuum-operated IP on a 15B.
Of course in the second video, that 15B has the style that's on the side of the intake and then connects to the IP down below.
Weird.
I'm still not totally sure how all of the throttle linkages work on the different iterations of the 15B. In that first video I posted you can clearly see the guy revving the engine up and down using something that goes down into the intake tract. I don't see anything else connected to that, either. You can also clearly see the PCV hose goes into the intake right there too, so they must be using some sort of vacuum there to pull out crankcase pressure. Although that was an N/A 15B so perfectly feasible. But it just adds support to the idea that there might be a vacuum-operated IP on a 15B.
Of course in the second video, that 15B has the style that's on the side of the intake and then connects to the IP down below.
Weird.