So my Evo has been sitting for awhile (3months) and recently replaced the mini battery in the car. The AFRs seem to be all over the map now. However at cruising speeds it's running as low as 12.2-12.8 consistently...not just slight blips. When starting to get on the gas it's going as low as 9.0. Also when going full WOT (though not very long) it's running around 10.7. Now keep in mind that before the car sat, it was running tip top all around.

So with the car running rich, is this a result of a boost leak somewhere? The car sat with mainly race gas in the tank and it's about 1/2 full. The car starts instantly and idles but the AFRs are not at all correct now.

 

I would do a boost leak test like you mentioned. What was the temperature like when you were tuned last? Possibly the temperature is really throwing the afr around.

 

Temps at tune were probably in low 80s (about 3 months ago) and yesterday was probably high 70s.

 

boost leak test! something is loose somewhere check all your vacuum lines

 

Have a new coupler for testing and threw it on. There was no air getting to the MBC. I could hear air somewhere. Just need to make sure it isn't the new coupler and the take the front bumper off to easly get to everything. Hopefully just a bad coupler.