Look at it from the O2 sensor's point of view...It has to work in a 600°+ harsh, toxic environment all the time getting covered in combustion by-product and soot. Then when we're done abusing it we let it sit in the dark and freeze (compared to the 600°+ environment. Wouldn't you get lazy after several years too?
But I digress, lol. Anyways, check the Ebay for the L1H1 sensor and try for one that is about $180.
And thanks for the recognition, SVOboy, I try my best to provide good info for everyone to enjoy.
Alain - Welcome to the site, and check out the VX info and links in my signature, it will provide hours of reading and info.
If the 02 sensor is original with those miles on it, I agree that it is probably the culprit. Did you use the specific plugs the car calls for with the specified gap? If not, I would switch to them. From my experience Honda's tend to run best on NGKs.
Car looks very good!
On the never-ending quest for better gas mileage...