[baldlobo]

01 4x4 sport qc sb 360 auto.
265 75 16 tires(31.5" tires not 33")

engine mods
no muffler 3 inch exaust (to each their own)
modded tb cai(to each their own)
New front 02 sensor.(will help)
Hughes plate(throttle body spacer?)
superchip87 tune(not sure if it does anything)

outward appearance mods
Testing partial grill block and bumper block.
Has shell or soft cover (tonneau cover?)

i'm thinking you have a vacuum leak somewhere in your evap system. 2001; it's possible either the rubber or steel tubing developed a hole(mercedes-benz likes plastic lines instead of rubber :P)

do you have a check engine light on?

have you reduced your speed?