So I finally had to put a little bit oil on the O-ring to have it fit into the hole: to hard without.

Sorry for mechanics recomendation, I am doing all myself.

First impression after injector + insulator and O-ring change, and mixture adjustment, the car had a better response to throtle:

- significant at lower RPM (feel more torque under 2000 rpm),
- on the highway in 4th gear, at 60 mph,

basically a better response (less lack) and better acceleration.

Need more time to see if MPG is improved (I had a bad one).

Still have to fix other problems...

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From 300CE to SLK230K