Globally they are working - but require decoking as regular service. even the new BMWs have this issue and dealers do the shell blasting cleanup of their intake ports usually. The reason for the coking up is that there is no fuel to wash the intake ports as the fuel is being just a few moments before spark - toyota have a clever design which utilize port and cylinder injectors both - the port ones keep the system clean.
Because this engine operates higher compression ratio - it will naturally make some soot, and because its a lean burn engine it is highly prone to knock thats why it requires a huge EGR system, as usual the PCV is plumbed into the intake, this causes a sticky carbon party to start when the sooty hot exhaust mixes with oil fumes from the PCV.
For this reason the engine oils recommended for these engines are quite unique. Yet the engine still requires decoking every 50,000 kms.