www.rx8club.com has tons of info and will answer all you questions.
The RX8 ECU is installed into the black plastic box on the front, passenger (US) side of the engine bay.
ecu?
buy a new one
Passenger side, under the hood, beside the radiator reservoir.You will see a black plastic cover about 6 inches wide by about a foot long, with three small bolts holding it down.The ECU is under that.
you'd have to get the tire size. It's on the tire itself.
check your coils for spark.if there ok replace the plugs and wires
You bring it to a mechanic..
replace ECU with identical ECU
To replace the ECU on a 2001 Miata, first disconnect the negative battery terminal to ensure safety. Locate the ECU, which is typically found behind the passenger side kick panel; remove any screws or clips securing it. Disconnect the wiring harness and any attached connectors, then remove the old ECU and replace it with the new one. Finally, reconnect the wiring, secure the ECU in place, and reconnect the battery before testing the vehicle.
Well fiery thing you should do is get you mazes rx8 back because it worked in it
The ECU part for this car runs $150 to $300. To replace it, it can run the cost up another $100 to $200 if a person does the replacement at a shop.