[Mykk]

2009 GMC Sierra 1500 SLE 2wd ext cab, 5.3L/4L60E

I have a small PCM tuning business so I wrote a mild 87 octane safe computer tune and I'm averaging 23mpg of mixed city & hwy but mostly in town surface streets.

I've disabled all of the torque limiting tables, all the ignition timing retard control tables (except for knock), removed all the electronic throttle limiters and dialed back TM. I figured any time ignition timing gets retard it's wasting fuel due to reduced power output.

I've reserved the DOD until 60mph and it shuts off with more than 10% throttle. I added a couple more degrees of timing and redid the transmission shift tables with the TCC apply tables. I've drastically increased the TCC PWM % minimums so there won't be nearly as much slip allowed in the drivetrain without making the TCC feel like the trans shifted into another gear.

I modified the air box to grab air from the space in front of the wheel well. Next I'm thinking of cutting out that big OE muffler and just welding in a 18" magnaflow for sound. The straight through design should help with exhaust scavenging in an otherwise stock system too.