* Minor Internal Components: Changes in piston design, connecting rods, or other internal parts could have altered performance or efficiency slightly. These changes are often not visually obvious without disassembly.
* Emissions System: Emissions regulations tightened over the years, so the 2000 model might have a slightly different exhaust system or catalytic converter setup.
* Computer/ECM Calibration: The engine control module (ECM) programming could be different, affecting fuel delivery, ignition timing, and overall engine performance and emissions. This is a significant difference, even if the physical hardware is very similar.
* Sensors: Some sensors or their specifications might have changed.
Without detailed specifications for each particular engine code (found on a sticker on the engine or in the owner's manual), it's difficult to specify *exactly* what changed. However, it's safe to say that some differences exist, likely subtle but potentially important. They are unlikely to be major architectural changes, but the cumulative effect of minor alterations is possible.
