1- the pic is from Chris' Lanos during the head gasket job he did.
2- the intake gets oiled up due to the crank case breather so this is a normal consequence... some people put an oil catch can to reduce the amount of oil being spitted into the intake.
3- i have cleaned my intake before and it made the car perform better.
all i did is get the TB off the intake (i cleaned it as well) and then sprayed all the interior parts of the intake with GUNK carb medic till it was crystal clean... now all the dirt have flooded into the bottom of the intake and into the combustion chamber.
http://www.gunk.com/CAT_M4814.asp
i then sprayed some fuel into the intake to wrens the passages and accumulate the dirt at the pistons then i removed all 4 spark plugs and the coil pack socket and cranked the engine.
the pistons forced out the dirty fuel/carb medic mixture out of the engine and the chambers are now empty... i left the spark plugs off for some 15 min. to evaporate any extra fuel then put every thing back on and tested the car... all that dirt really robs from the car's performance.
if you ever though of doing that remember to do it on a cold engine, remove coil pack socket, do it in a well ventilated space and keep a fire extinguisher handy.
it seem like a crazy idea but it really works and the other alternative would be taking the whole intake off the car.
MMamdouh