If your 1997 is like my 1998 C230, those outer slots in the airdam vent cool air into the front wheel wells - whether to cool the brakes or to equalize pressure areas is not completely clear. I wouldn't want to fill them myself, I would move the lights inboard to the center airdam slot, or possibly a set of the Hella Micro xenon driving or fogs behind the grill.
Wiring additional lights would be interesting. The safest bet for your existing wiring, fuses, and switches would be to have your existing fogs switch on a relay that fed current from the battery to the aftermarket fogs. Since your battery is in the trunk, this wiring will be more difficult, as it invilves running heavy gauge cable from the battery to the relay, from the relay to the aftermarket fogs, as well as lighter gauge wire from the relay to the existing fogs.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
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