Question about ECU and tire size

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2002 Protegé5
So Im considering putting the Mazdaspeed wheels and tires on my P5, but Im the type of person to want to have my speedometer and odometer stay accurate. With my Chevy truck, tire size can be programmed in the ECU by a dealer, though Im unsure if thats possible for the P5, and one dealer told me it isnt, despite my hearing mixed things on forums. That said, my other curiosity is if its possible to take an MSP ECU and reprogram the ignition timing and fuel map so it works fine for my NA P5 and runs 87 octane well.

Any thoughts or insight?
 
You can't program the PCM.

The MSP wheels and tires are close enough in diameter to the stock setup that there's no need to anyway.
 
Someone reminded me of the Yellow Box speedo correction thing, so I can fix it anyway
 
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