If you really want to 'go to town' on it then you could remove the inlet plenum which sadly is also part of the rocker cover. You will need new gaskets but can take it all off and give it a dam good soak
I just got an old tooth brush and sprayed some cleaner up there and poked about with the tooth brush pulling huge clumps of carbon out. The first start up has a nasty tap for 1/2 a second and then all fine, just where the cleaner has removed oil.
I was thinking the other way of cleaning in there is to take the air filter off and run the car at 2k RPM and pray cleaner into the air filter. that should clean some carp out of the inlet....