The throttle switch on D-Jet doesn't really do much at all. As already mentioned, it just adds in some extra injector fires when the throttle is pressed open (sends additional signals in the same manner as the triger contacts in the distributor - the printed circuits alternate the extra fires between the two injector banks). The only other thing the throttle switch does is close a contact at idle (throttle completely shut) that triggers the special idle tuning. This makes the box respond to the little adjuster on the computer box. They hand tuned each car at idle at the factory to make them clean enough to pass the emissions regulations without needing extensive detuning or air pumps or any of the other junk other cars needed at the time. Without the throttle switch it just stays on the 'canned' tuning map, which is so close you probably wouldn't notice the difference without an exhaust sniffer.
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I'm JohnMc, and I approved this message.