the way i read your post, when you got the retune is when you started seeing the loss in MPG..

Put the stock intake back on and clean the maf again, and run a stock paper airfilter.
i went from 14mpg to 17.5mpg average just from retuning and driving a lil smoother in my truck and its got a 6.0, isky turbo cam, 4L80E and 3.42s.

 

good reason for a Wideband.

 

Well I originally lost MPG with the K&N, after the tune I let things settle down for a few months and I feel like I've lost another 1-2 mpg with the tune. I just don't want to blame Nelson for anything. I'll put the stock air box back on tonight.

Change of topic, if I can, does a wideband replace the stock O2 or is it in addition to it? Do I have to make a new bung in the exhaust to install one? I don't think I can do that without outside help, which I'm trying to stay away from. But it sounds like a wideband could be worth it...

 

You can replace one of the stock ones with the plx and use its 0-1v output, but most other widebands dont have that.

 

Thanks for the guys who commented on this, sometimes the obvious is hard to see until someone tells you to look.

I posted about my K&N removal tonight on my other thread about the FIPK... I think that thing is the source of all my problems. The truck drove better without the K&N on my short test drive tonight. Looking forward to seeing MPG results.
https://www.performancetrucks.net/fo...-497418/page2/

 

the only way to really know is with a wideband. weld a bung in before the cats. if you think about how our trucks pe structure is set up it makes sense that mileage would go down with a performance tune. gm did a fairly good job at getting a 5.3 pushrod motor to get 20+ mpg in a 5000 lb brick.

 

Hey KC Kid I see you live in Lenexa. I used to live in overland park and shawnee. Did you happen to go to shawnee mission west high or what is your name. Just trying to see if I know you.

 

No, I grew up in southcentral KS, went to KSU forever then moved to Lenexa in 2008 to start working.