So I’m noticing that this is the same vacuum switch that is also on the throttle bodies, but this one under the seat has no line connected to it? Is it supposed to have a vacuum hose connected to it and if so... from where?
Location: In the twisties around Hendersonville, NC
The other one is the Intake Air Pressure sensor (IAP) and it is there to measure the actual pressure in the manifold between the throttle butterflies and the intake valves. It needs to be hooked up to the hoses going to each throttle body.
Cracked or loose hoses to the IAP are another area to check for strange running problems.