with the maf enabled, the maf does the air/fuel cals. front o2 are for checking if your at 14.68 a/f with maf enabled. rear or after cat o2's are for checking to see if cats are working. Which why it still runs good with maf enabled cause its doing the A/F.

just a note

 

So how is your denali treating you? Just wondering, right now I am only pushing 18K on mine.

 

off topic here.. but did u happen to be in the buford area yesterday? A black denali flew up on me on a two lane road and threw me a few revs, wondering if it was you