1996 C220 evap problem
 

Hi i have a 96 c220 and the check engine light is on. i checked the code on the the obd tool and i get P0441 which is Evaporative Emission Control System Incorrect Purge Flow. I'm wondering where this is located or how i can fix this problem?? im getting alot of up and down reving when im at a stop, could this be the problem? thanks i would appreciate some help

Purge valve is by the windshield washer reservoir on the left frame rail...has the letters "MOT" on top.