Interesting article on Daily Tech today looking at the potential for power loss over time in DI engines due to carbon buildup on intake valves:
http://www.dailytech.com/Direct+Inje...ticle21962.htm
The article provides dyno readouts for an Audi RS4 when it was relatively new and then before and after engine cleaning that show a dramatic power loss which was then reversed by the clean. A good discussion follows.
It's claimed in the discussion that the use by Toyota of port injection at low power and idle alongside DI in its current DI engines allows the cleaning agents in the fuel to wash the valves regularly so this may not be an issue for the FR-S.