The EHA adjustment is VERY critical on an oxygen sensor car!

IF the differential pressure is more than the original 0.4bar that is pre-set by BOSCH then the O2 sensor will have to control the mixture more that it was designed to do.

Since you adjusted the EHA a 1/4 turn I would imagine that is happening on your car..

I always suggest that adjustment to be no more that 1/6 turn unless you have fuel gauges to see that differential fuel pressure.

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