3g hemi gas mileage

5.7 hemi said
Alrighty lets try to get some of the questions answered.

03' hemi 545rfe trans, stock computers (althougth I raised the shift points and firmness)
28 inch tall tires, 6.1 injectors, TTI headders with x-pipe exhaust, car intake manifold, 3.91 rear gears.

I switched the o2 to the passenger side per Chris at hotwireauto.

After much thought on the injector size, I might be to big with the 6.1 injectors so I'll switch them back to the factory 5.7 injectors as johnparts has eluded to.

The 03 hemis use only 1 o2 when using the aftermarket harness from hotwireauto, 04 and up use 2, again per Chris at hotwireauto, besides, I did try both and the engine ran like ****.

Gonna back flush the block tomorrow, so I'll switch the injectors at the same time.

Right now you fuel map is opening injectors longer then they need to be opened because the 6.1 injector flows 32.3% higher flow then the 5.7 injector this is problem #1. Problem #2 is I don't think the system your running is allowing closed loop fuel trim adjustment with a single o2 sensor. So you need a wide band o2 to see how rich you are running and adjust the tune accordingly if you have the ability to modify the tune. That's why I really want to run a factory PCM and harness in my build and that's why I don't have a running engine right now. Chrysler spent years on the factory calibration to get 20+mpg. So if you can't tune it make sure it's completely stock or you will never get the mpg you expect.