If you wish to adjust the mixture by duty cycle you definitely need to leave the O2 sensor attached.

I'm not sure what isn't working, in a post recently I forgot to point out that one needs to push down on the adjusting device to engage the adjuster. The other issue is that late models that have the led diagnostic on the passenger side mnust have the diagnostics activated to get the duty cycle read out.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician