As far as I know, disconnecting the wire from the negative terminal for 15 mins or more forces the computer to re-learn when you fire it back up. If you're looking for more radical changes I think you can get a custom programmed superchip... but with just exhaust it's probably not necessary.
when you unplug the battery, it doesnt completely delete the ECU, it merely takes out the programming that controls AIR/FUEL MIXTURE. the ECU also controls the odometer, the ABS, and the AIRBAG, and you can leave your battery unplugged for 2 years your odo wont reset. the system has three lithium ion batteries that run in series with the standard battery. they will trigger the ABS and the AIRBAG if power is lost. they will also automatically roll all the windows down immediately after an accident so you can get out. to COMPLETELY reset the ECU, you need to pull it out from under the passenger dash, pull off the cover and pull out the 2 batteries that are there. the third battery sits in the ABS system somewhere. but theres really no reason to do this.
Actually, the Ford 2000 Service CD says that if the battery is unplugged for more than 1/2hr It can cause 'problems' with the odometer and settings for the car. It states this because under the list of what not to do's it says Ford is not responsible for service on the car if the battery has been disconnected for more than a certain amount of time.
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