This ICM maintenance DIY was contributed on Audiworld by PartyBoyRacing.  I have added pictures.

The Ignition Control Module (ICM), also referred to as the Power Output Stage, are mounted on top of the airbox.

The ICM must dissipate its heat through the heat sink which is embedded on top of the upper airbox housing (the ICM mounting point).

The ICM transfers its heat into the upper airbox heat sink. This heat is then dissipated away from the heat sink by the air passing through the internal portion of the upper airbox heat sink via the engine air intake.

For optimal thermal dissipation, the entire bottom metal surface of the ICM must make solid (and flush) contact with the upper airbox heat sink.

This is accomplished with the assistance of heat conductive Silicon-based Heat Sink Compound. [Note: The site author of MyAudiS4.com used a different type of thermal paste.]

A good thermal/mechanical connection between the ICM and the airbox heat sink may prevent premature ICM failure.

PREVENTATIVE MAINTENANCE TIP:

Eventually the factory installed Heat Sink Compound will harden and loose much of its thermal transfer capacity (time depends on environmental conditions). The ICM should be reseated with fresh Heat Sink Compound as appropriate to provide the ICM with the longest lifespan possible.

GooGone removes the old Heat Sink Compound well, followed by a quick drying electrical component cleaner to prepare the surface for new Heat Sink Compound.

DO NOT scrape or gouge either the surface of the ICM or the surface of the airbox heat sink. Doing so will reduce the thermal transfer capabilities of the ICM heat dissipation process.

Apply enough compound to the metal base of the ICM to ensure a complete bond between the ICM and the airbox heat sink.

Then torque the ICM bolts to spec.