You're probably asking, "what's this stupid thing for?"  Nothing really, just experimenting with the electronics in the vehicle.

Once the engine is at normal operating tempurature, I can reduce the RPMs from 800, to 500.  If you are stuck in traffic, and do not want to turn the vehicle off, simpply cut the RPMs, and you go into silent idle mode.

The engine is very quiet, depending upon the noise level from inside the engine.  However, overall noise is reduced.

With the K&N cone I put on the end of the plenum, you can hear the air being sucked in at idle.  When you use this cut-off, you no longer hear that noise (where it mostly comes from).

First, notice the hose that comes off the plenum, right where the COIL wire dips down.  This is the air-flow to the valve
I am talking about.  This air bypasses the TBI bore, straight into the intake.  The "Air-Valve" is supposed to close when coolant temp. reaches 145-F, but mine never does close.  There is a lot of air being pulled through here, maybe a future forced air pump add on in the future. . . (Compressor, and air-tank with control valve. . .  Sounds neat, or to inject Propane???)

On the TBI unit, there is a plug to a cylinder; it is right in the center of the picture above.  Here is another angle:

See a larger view
You can see the blue plug better at this angle.  My wire (4 Conductor Telephone Drop Cable, nicely shielded, and weather-proof), you see it leaving the plug to the left.

All my wires run through two pieces of 1/2" grey "flex" conduit, and one piece of 1/2" EMT.  They are nicely connected at the fierwall, through holes arelady there, with the proper fittings placed in the holes.

I cut the top wire on the plug, and ran each cut end to a SPST push-button switch (not a momentary trpe) on the dashboard:

Just a tiny one, huh?

Other uses?
If you leave the switch in the on position (open circuit), a cold start will be very difficult.  The vehicle may not start at all.  It can be used as part of an anti-theft device (hooked to a relay with an alarm system with an ignition cut-off circuit).

Sometimes, the air-valve this thing is connected to will not open when you turn it off (closed circuit).  You only need to try it again, till it's does.

You can accelerate, but with greately reduced horsepower while the circuit is open (valve closed).

Rapidly pressing the gas pedal on and off will cause it to stall, or go below 400rpms momentarily, for which the Check engine light will illuminate.  My check engine light does not come on when I use it to reduce the RPMs only.