Like in Audi FSI motors, build up of deposits on intake valves and ports at around 30-40k miles in the N54 engine is a known issue and it is still an issue for MOST direct fuel injection engines.
However, in the case of Toyobaru's D-4S injection technology, direct injection is combined with port injection and since gasoline is a powerful solvent when injected during the port injection phase it can prevent any contamination and sooting up the intakes. No oil catch cans will be needed then
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