Is it just a "pinch" and pull? Meaning, squeeze the wire end to lift it over the nib on the car end plug?
I tried today, without success...Can't get any leverage with so little space! I can only get one hand near the plug.

 

I was finally able to "pinch" the connector enough with needle-nose pliers, then used a long screwdriver to push it completely off. Note to Honda: put those connections high up on the firewall!

 

Finished installing the exhaust system from the downpipe to the muffler, all new now...

Still have to re-install passenger seat after plugging in the O2 sensors.

 

Started the car up, and drove it a short distance: so far, so good!