2004 Base A/T
Relevant mods include:
Manzo Exhaust Manifold
TurboXS CatBack W/RacePipe
Stock air filter box with the RB REVi intake duct
Stronger fuel pump Installed in Stock housing
Always running Shell 91 or Sinclair 93, but generally Shell 91 octane on every tank.

I've now tested out on numerous different maps on my COBB, including the MM base calibration and with every one when I let off the accelerator, my AFR jumps to 20.4 or more. I've looked in the forums here and that seems a bit excessive to be normal in any scenario. During acceleration and Idle it hovers around 13.4-13.8, which I'm happy with its just odd that it leans out so much during deceleration. Any input is appreciated!

 

That's exactly what it's supposed to do. Injecting fuel during deceleration = pouring gas out your exhaust pipe.

 

thank you for the Info!