I disconnected maf sensor and duty cycle went to steady 59.7%. When maf is connected cycle goes to 50% and going down to 3-12%. I have O2 sensor on order. It will not hurt the car to have new O2 sensor since it's old anyway.
I did have a stalling problem before and I bought a used maf from good running car with 125k. I know the guy and it was his personal car he parted out. After maf replacement my car never stalled once. Maybe his maf was not good?

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod