How do you know if the odometer has been tampered with on a mk4 supra
 

I replaced the plastic clear dash speedo cover in my car. I had to unhook the odometer to get at it. I then drove over to the parts store to buy a light to go inside my boost control as well. i came back hooked it all back up and finally didn't realize until today that the odmeter wasn't hooked up on the car while i took it out to the parts store. Does the computer make up the difference and know it has been driven. This is a very bad feature on this car. I just bought it and how the hell do i know if the actual mileage is correct.

Agreed - the car can run without the odo plugged in. Worse yet, you can swap the odo and it won't throw any codes. Best bet is to track the carfax and any emissions and maintenance records, and carefully look for any discrepancies.

On the plus side, I believe it won't rev over 5k with the odo unplugged, so at least you know the engine didn't see any hard miles with it in that state.