If I am not mistaken, don't all of the (W210) cars have an air filter?
To change it, I believe you have to go through the glovebox.
1994 E500 (MY SUNDAY DRIVER)
1993 190E SPORTLINE LE W/ M104 SWAP
2000 BMW 528I (WIFEY'S CAR)
"Excuses are crutches for the unfounded."