Hey all,

I just got back from a dyno shop and like many others use the wideband up the tail pipe to determine a/f ratios. I also had my own wideband installed but on the header (before the cat, stock o2 location). During the dyno, the a/f between the two would vary as much as mines reading 1.0 point richer than the dynoshops'. If you were in my position, which would you trust more, the tailpipe or the precat? does it even matter? and why would the tailpipe read leaner?

Thanks