You should release a colony of fruit flys under your hood to eat the gum residue.
After that, a few small lizards to eat the fruit flys.
Then a snake to eat the lizards.
The fattened snake will curl up under your air filter until he's ready to shed his skin, at which time he'll crawl out, scrape his old skin off on your fan belt, and leave.
Then all you have to do is get the old snake skin off your fan belt. Maybe a stick with some gum on it would do the trick.
1999 E320 Wagon