07 tundra bad mpg, A/F ratio is 8 and power loss till 4500 rpm

I have an 07 Toyota Tundra. I have a Bully Dog tuner. Cat-Back exhaust from Corsa. Cold air intake. I'm getting 12 miles per gallon and if I jump off from a dead stop. The truck seems sluggish until I hit 4500 RPM. I've been looking through the Forum and reading that it is a Toyota program that adds more fuel 2 offset the more air I am getting now. The truck seems to have less balls now then went it was stock. Does anyone have any ideas how I can correct this issue. The math has been cleaned and so has the whole throttle body

 

Opening up the exhaust will remove some low end torque.

 

Remove the BD tune and see what happens.

Larger intakes, higher flow exhaust typically mean less torque and "more" HP....which sounds "like" what your experiencing.

 

@dirtydeeds

 

Yep I have removed the BD tune. And that was no real change. Also if I'm driving. Say I'm doing 60 miles per hour stuck behind somebody in a 70 mile per hour. When I jump on it to go around. I downshift 2 gears and it's as if I create a vacuum lock. I've got no power for about 3 seconds and then it jumps. My air to fuel ratio is 8. And it should be around 14. I'm running extremely rich right now while driving or at idle. Also I went from the 2 and 1/2 in stock exhaust to a 3in catback Corsa exhaust. I did not bore out the cats though. I was told my truck needs that back pressure

 

WOT I'm .8 lambda which is low 12s AFR.

Have you tried running the truck after a hard reset? With a stock intake? Exhaust is a touch harder to revert back to stock for diagnostic purposes.

 

Did you get that 8 afr from the Bullydog? If so, I don't think I'd believe it. The bullydog for my supercharged Tacoma always shows 8 even when an independent gauge shows it varying between 11.9 and 17. I don't think the bullydog reading is correct.

 

I guess the next question is why does the Bully dog show 8 for both A/F ratio sensors? I'm looking at this now in my supercharged Sequoia. Solid 8.

 

Spark Plugs??? I know it sounds dumb but these trucks are known to behave strangely when plugs are getting worn. i.e, poor mileage, power loss, weird shifting... all things I have heard associated with plugs going bad.