Running a tune by mac auto in parker co on 91 octane. Just put in a wideband and found out that I'm dipping under 10:1 pretty much at all times in open loop. Nothing has changed on the car and I just checked for boost leaks and cleaned the maf. My question is; since I have a cat is the up-the-tailpipe wideband they use less accurate because of the cat? And am I seeing more accurate readings? Should I start looking for mechanical issues or work things out with tuning? I'm thinking the ladder at this point.
Oh and I'm looking at the dyno print out that shows a solid straight 11.6(ish):1 afr.