94k miles and its slow as a dog at start up and im now getting 9.2 mpg (over head) ficm tested out good 47.x volts truck has a new hpop a new icp a ipr and icp pig tail so now im at a loss here... no check engine lights either any ideas truck is a 2003

 

We're in the same boat... I've been trying to figure it out... My next move is to get my PCM rolled back to a different strategy...

But now I got a bad gpcm...

 

my truck was hard to start
found out the batteries were not 100 percent
changed both and ....wow ....starts up fast...what a difference
maybe you have a bad cell
one battery is bring down the other one....

I also changed to the swamps 58 volt FICM
last winter

 

It is amazing what poor batteries will make these trucks run like. Poor starting, poor idle, make the trans shift funny etc...

 

i have 2 optima yellow tops that i just got in january so im sure the batteries are fine

i just ordered rev-x and 4 gallons of shafers full syn also i noticed my intercooler boots are really squishy and one is dripping oil i ran a scanner on my truck and my boost was at 21psi which the guy told me was low so im assuming a leak reguardless i bought some bd performance intercooler boots with t-clamps just now too i was gonna get the riffraff boots and use the stock clamps but i might as well do it right and do it once and i read good things about them. just racked up a 400 dollar bill in all but hopefully this helps

also last night i went up this mountain trail by my house and its kind of steep driving down so i didnt wanna burn up my breaks so i used 1st gear all the way down (30 min) after i got on the road it was driving kind of weird almost like it was in O/D... i only put it in 4high with the hubs locked 2 times and rompped on it a little. after i got back on the road i tried to 4wd power break it and it was taking a while to get it to 2k rpm then once it did it dropped a little so i took my foot off the throttle because i got a little scared... normally ill cherp the tires a bit this time however it took off like i was towing a trailer... any ideas?