1994 honda civic ex 5 spd
 

I was wondering if it was possible to use a VX oxygen sensor and VX ECU to get greater gas mileage? If this is possible, where does the 5th wire for the oxygen sensor hook up? I have recently been getting 30-33mpg Highway with a completely stock 1.6 SOHC vtec (172,000miles) with 1996 honda civic HX 5 spd transmission and am in need of better mileage.

Thank you in advance.

Better mileage is going to be in your head, in your gearing, in your intake and your exhaust as much as it's going to be in the lean burn.
the VX tranny is going to give you better gearing then the HX even but your 1.6L engine most likely has a cam that is giving you lousy low end power and because of that running rich, to match low end power you need a tuned intake and exhaust that is matched to the engines lower speed.