Inconsistent WOT AFR's
 

So most of the time at WOT my Evo will hit the numbers it should be (12ish coming down to 10.9ish around redline) but sometimes it will run a full unit richer than the target AFR. The only code I have had come up is VSS (vehicle speed sensor). I was certain that couldn't be the issue but I have replaced so many components and I recently saw someone say replacing their VSS fixed a similar issue. Does anyone else have any experience with this kind of situation, and have a possible fix?