Thought I'd add my results.

I bought my IX a year ago with an old JB tune. With my AEM wideband I could watch the A/F sit in the 15.5 range cruising on the freeway or when I had enough load in the city which usually took a slight hill. My MPG was 16-17/25-26. City is low because I have a 2.5 mile drive to work so I spend a lot of time in warmup mode.

Recently I switched over to tephra V7. I noticed during cruise my A/F was 14.5 (My gauge is probably slightly off as that's what it is at idle as well). MPG results dropped to 20-21 mpg on the freeway. Ill go back and set the appropriate tables from Aaron's old tune in the new tephra maps and see if that gets me my extra 4-5mpg back.

 

Little Bump for info

I dont have an EVO, just a DD 03 Stratus 2.4, working on flashing it for better MPG. Anyway is there a reason that I need Closed loop at all? as in why do I need closed loop? Is it mainly for Idle quality or what?

I know the fundamentals of tuning, as I have a standalone on my other car:
http://www.cardomain.com/ride/2641801/1989-dodge-spirit

 

Very nice write up