06 VW Passat - Intake Manifold questoin

Car dumbie back again with another question.

The diagnostic for my check engine light indicates numerous cold start misfire codes. The cylinders are OK. That was checked during the diagnostic.

The fuel intake is carboned up. It is recommendded that I clean the intake manifold. Does this mean cleaning the fuel injectors, the throttle body or both? How much should this cost when done by an independent mechanic (ball park)?

The car has 58k and they told me the spark plugs are fine too.