a few other things to note about this system.
this system will give the idle speed only if there is any problem with the accelerator pot, which includes if the setup with the computer is set close to the published specs, there can be a real lead foot that bends down the accelerator pedal and creates a reading that the ECU thinks is the accelerator pot out of range, and then shuts down to idle only, and if someone messes with the pedal stop bolt on the floorboard under the accelerator pedal trying to get the machine to go faster, that can set the accelerator pedal out of range error too.
As Jplayer noted, the new ECU does not require the vac hose, and you can tell which is the new version, when you look into where the round cover that you remove to hook up the computer, if you see the resistors, transistors and diodes, then it is the newer version with the electronic MAP function, and if it is all beige/white plastic "potting", then it is the older version that NEEDS the vac hose to be right and on the correct port of the throttle body.