I know it wasn't your issue, but I figured I'd add to the initial O2 sensor location discussion. If you run an electrically heated O2 sensor, you can put it further back without issue. Think of the wideband probe a dyno uses, they put it in the tailpipe and it works fine. The 9-12" is for non heated O2 sensors which only read right when they are hot enough. Put them too far from the exhaust ports and the sensor will never heat up because the exhaust gasses have cooled too much by the time they reach the sensor. With a 3 wire or more sensor it has a heater so there's no restriction on placement.
