Hey all.
I've got a 4-2-1 header and the O2 sensor is in the 'stock' position. That is, it's about 1/2 way between the ports and the collector, after the 4 primaries merge into 2. Since the sensor is only in 1 of the 2 tubes (it's only reading ports 1 and 4), would this have a negative effect on the computer's ability to correctly adjust fuel? The reason I'm asking is because I noticed that the inside of the pipes for ports 2 & 3 (the ones not read) were very black & kind of sooty, wheras the ones where the sensor is were relatively clean. The plugs all look fine, got a medium tan color. The ECU can't determine rich/lean conditions for individual cylinders, can it? My understanding was that the sensor reads either rich or lean, and the ECU corrects accordingly across the board.
I thought this may have something to do with why I get popping from the exhaust (too rich??). Usually happens between 2900-2500 rpms when decelerating.
Thanks.

Nope, it still reads the same.