I paid attention to the instantaneous mpg display on the way home and it is definitely cutting the fuel supply. mpgs go to 99 until slower speeds (when it slowly increases fuel to keep the engine running). I guess what I'm missing from the equation is the cylinder shutoff, like you thought.

I won't ...

When I feel the engine braking kick in it doesnt enter V4 mode, at least the display doesnt indicate it. I figured it was mostly injector cutoff. So nobody else has reported this?

I finally decided I was tired of AFM. Contrary to GM's claims I can feel it when it is engaged and there is a noticeable lag when it disengages. "Feel it" is understating it, more like hearing a loud rumble, and a strong vibration like the engine is detonating.

So I changed my tune parameter last ...

Try all of the tunes. I found my best mpgs using the 87 tune, better than the mpg tune.

I bought this tuner for the same reason (6k camper) and just went through an 8000 mile trip over the Rockies in July. After a lot of testing I found my best combo was the 87 tune with high octane when towing (87 octane when commuting). That eliminated the worry about getting at least 91 octane gas ...

See my thread on this topic.

I've pulled my 6000 pound camper 8500 miles all over the US using the 87 and Diablo tunes. For several reasons I've settled on the 87 tune using 87 octane for daily driving (got much better mpg than the mpg tune) and the 87 tune using high octane while towing (slightly better mpg and no need to ...

After a lot of testing between mpg, 87 and Diablo tunes, my best one for economy was the 87 tune.

After towing over 8500 miles from the east coast to the west coast, up the west coast, and back to the east coast, I have some observations. 2010 Suburban, 6000 pound camper. My primary goal is towing performance and I originally bought the tuner to adjust the fan temp settings (as discussed ...

Glad to help. I've been insanely busy the last 3 months so hopefully I'll get some down time next month so I can run some tests. I need to wire up some indicator lights to the relays so I can tell when the low and high fan settings have been activated by the computer, then start modifying the fan ...

91+ octane performance tune.

Doing lots of towing right now, I've noticed the same thing, with the 2-3 shift very hard compared to the 3-4 (and higher shifts) at full throttle.

I know about the various protections, like turning off the A/C once you hit a certain temp limit. I've hit that twice on this trip, both times the A/C came back on in a minute or two. No reduction in power warnings, that is a more severe overheating condition. This happens on every long pull when ...

Will post when I can, currently on the road for 3 more weeks so online time is limited. I can confirm I see the same thing in the 87 tune, I had to switch to it a day or so ago as I approached the Rockies where 91+ octane isn't always available. I've actually experienced a slight mpg increase even ...

See my thread about setting fan settings, the percentages are largely useless for older vehicles, only the newest use PWM to control the fan speed continuously. I still need to run tests to see which percentages correspond to the low and high fan speeds (and for a few model years, a medium setting ...