Cant help you there. but will give you a pat on the back for actually reading the directions... so many mechanics I know think they know it all and do a worse job than DIY'ers whom follow the directions..:mad2:
towed a couple big bobcats to a job site. guy said they weighted more than 16k on the scales without fuel or trailer. They had some pretty sweet attachments on them too. oh and my LB7 didnt even break a sweat....
honestly. maybe 1 mpg. I return an average so far this year of 20.43mpg and a high of 24mpg on a trip. I use virginiabeachgasprices.com fuel log to keep track of my mileage. The tuner set on performance has definatly been what increased my mpg noticably though.
I wouldnt see why not. you can get the gallon canned stuff at advance auto and just drop them in there for a while. did that with a carb that was so gunked up with that ethanol crap in our gas that the carb cleaner in the spray can wouldnt even touch it.... now it runs like a champ. at least...
if you have the money the 4" is worth it. not sure if you will see a lot of mpg increase with cutting out the muffler. you will get a very small bump in mpg with the 4" but nothing to write a book about. I think the duramax sounds awesome with a 4" turbo back compared to just a muffler...
there is no resonator or cat. Just a muffler unless it is cali emissioned. What are your intentions though? Just sound? Performance? EGT's? If your only reason is for sound then chop the muffler.
never flush a tranny! blew the seals out on my blazer with 80k on it! and yes i maintained it well prior. i would go with amsoil if you are keeping the truck a while and if not whatever you can afford...
with tuning a 6.5 will outpull a 454 handsdown. they may not make a lot of hp but make about 600lb of torque properly tuned and built. take a look at a few peoples 6.5's on here and read the 6.5 section. great workhorse unless its stock! nothing against the 454 at all though but with fuel...