Sputter

[kkritsilas]

RFI sheild almost for sure, being as close to the ignition system as it is (the very high voltage pulse that fires the plugs is an exceptionally good noise generator, and quite broadband (across a very wide frequency range)). The electronics are probably running at 5V, so the probability of its picking up noise from a >25 KV source are almost 100%, and let's not forget that there are 6 or 8 of these noise generators all around the module, along with the coil. If the "foil" is thin (i.e. relatively low mass. easy to bend) it is probably an RF shield; heat sinks tend to be thicker because they use their mass to conduct heat away.

 

[Darth-Car]

I know this referenced shield, since Darth Car has one. It is a honeycombed, quilted foil. That looks more like heat shielding then RFI. Plus back when the first Lean Burn systems came out, I saw many that had a strip of corrugated cardboard stuck to the bottom, by the owner to help with overheating of the unit.