The other weekend I put some mods on my 06' 2500 5.7 QC/SB. Optima red top, Bosch Iridium Plugs, MSD Coils, K&N 57 CAI kit, 180º Jet thermostat, Flowmaster 50 series cat-back and a Jet stage I chip. It took about 6 hours to put stuff on had help from my bother. I have a Fitch fuel catalyst that is still waiting.
Back a couple of months I did a highway mpg run just to see what it was for real. The only thing I did to the truck has been using synthetic oil from mile 18, I got 16 MPG
not bad for no bed cover on and driving like I allways do. The truck's read for over all is high 10's - 11 mpg.
I have not had a chance yet to do another run But the read out is saying 14.5