Progress is not always something that moves in the forward direction or for a good cause. Take the rise of the turbocharger for example. Even though it's made modern engines more powerful and efficient, enabling manufacturers to get the same performance out of a smaller package, the work done to make that possible was all due to tightening fuel economy standards. And those same guidelines are about to set back the clocks of progress for the M3 and M4.

One of the highly touted features for either car was the inclusion of a driveshaft made of carbon fiber reinforced plastic, which not only reduced the overall weight of the car by replacing a typically heavy piece of machinery with a lightweight composite, but it also added to the engine's rev-happy nature by reducing the amount of rotational inertia the engine had to overcome in order to transmit power from the transmission to the rear differential. Try not to cry a river, but that piece of exotic hardware will soon be phased out of the M3 and M4 and replaced by a more traditional steel driveshaft. The reason for this, as BMW claims, has nothing to do with the 2016 recall that covered the M2, M3, and M4.

Instead, it's all the fault of the regulators who require that the part be removed so that the current M3 and M4 can comply with emissions standards. It's not that the driveshaft itself causes the car to pollute more, it's that the mechanical demands of that part dictate that it must have a larger diameter, which apparently interferes with emissions control devices BMW will soon need to put in place to keep the cars legal. At a later point, BMW will install the Petrol Particulate Filters that will soon be required. BMW says performance will remain unaffected. What's more likely is that performance will be marginally affected but to such a low extent that it'll be unnoticeable to most drivers.

The change will only affect the M3 sedan, M4 coupe, and M4 convertible but will leave the M4 GTS and M4 CS untouched. There, now you have another reason to go shake your fist at the eco warriors if that's your thing.