So I've been getting my tune pretty well dialed in on my new engine, but one thing that has bugged me, even when I had the 305, is that when I let up on the throttle (low rpm 1500 give or take, throttle now closed) My Wideband just goes pig rich (10.5-11.5).
What is the table id use to lean this out? This is in open loop if that makes a difference.

 

This may be in part a deficiency in the TBI "system". Throttle lift induces vac and the wetness sticking to intake is released. Your WB is picking up the transition. DFCO will help but not cure. Port fuel is the answer to cure.

 

Interesting, So im wrong in thinking the computer is actually dumping fuel in when I let up on the throttle?

 

With TBI atomization is compromised. two injectors spraying on the circumference of the TB bore I wonder how many molecules are successful in avoiding the intake runners sides into chamber? At part throttle I bet 75% are on the runner and then being sheared off. Watch the MAP when you lift throttle is will spike to full vac. Wont take but a split sec to dry runners off.

 

Well when I lift the throttle, it shows 0 MAP, and the AFR stays on the rich side for quite a while. usually stays rich until I get back on the throttle.