If your car's multipoint fuel injection, the throttle body should stay pretty clean (the injectors are well past it at the far end of the intake manifold; no gas to bind dirt to surfaces; also the air filter does a good job keeping most of the dirt out).

Last time I replaced the head gasket on my D16A6 (at 160k+, I cleaned a bunch of builtup sticky black dirt (almost like slightly sticky asphalt) from where the injectors enter the intake manifold and some from the intake side of the head.