06Sierra2

with those big@$$ wheels i dont know how it could feel slower. I have some heavy 22s and i felt a big difference in acceleration after installing my 4.10s. Have you ever raced the truck at the track?

denali_on_26's

iTrader: (26)

no i have yet to run it at the track... i was just going off of feel.. the biggest feel of loss is from a roll like passing at 70mph...

offroadrider12

+1 I always thought best mpg was dependent on pulling the most vacuum. The RPMs at which that happens varies because of engine mods and other things IIRC.

Gordy M

iTrader: (2)

Reading this thread reminded me of when I bought my LS1 based car. I was used to the old school V8's on how they ran and what to change. Unfortunatley it amounted to "Read, Fire, Aim". You are chasing a host of inter-related changes to the truck and engine without knowing what they are doing to the trucks PCM/BCM/etc computers. For instance, when you changed tire sizes or addes LT headers did you change those sizes and air flows in the PCM. The powertrain is making changes to your engine based on the wrong info and is adding and subtracting fuel, increasing and decreasing timing and other changes.

Find a tuner who understands how to run a scan log and what the information means. This is the basis for making any improvements to performance, gas mileage, towing, transmission, etc. For example, my 6000+ Escalade ESV gets 14.1 in city driving 18.2-18.5 highway and 10.4 towing 7544 lbs of an enclosed trailer filled with a Corvette, tires, gear, jacks, etc.

denali_on_26's

iTrader: (26)

Yes changes were to the ecm for everything I had done....