difference between narrow and wide band A/F Gauges

.........and they haven't gone up much. I bought one several years ago it was near 200 THEN

Side note: Read up if you buy one. There are some things that can "kill" the sensor and they ain't cheap. If you aren't going to "need" it at all times (after tuning) you can remove the sensor and plug the bung. If you are "cheap like me" you can use a Ford 18mm spark plug. You can ALSO order 18mm nuts a hell of a lot cheaper than most bungs cost. I've forgotten the thread pitch, "been awhile"