I'm trying to get this tune dialed in. I disabled the maf to tune my ve tables.
Before I started, my ltft's were VERY high.
I ran a log on the way home from work, added the histogram to my VE, reset fuel trims, ran a log to work, added my ltft to my ve, rince and repeat.
Problem is my ltft's aren't really coming down.
I put my thinking cap on, and came up with an idea.

I got my PCM from brads's old 1500hd. I had it reflashed with a stock tune for my '99 and my VIN.
I know '99 had smaller injectors than later models, so my idea is.....
The PCM is tuned for the larger injectors, so the PCM is thinking the injectors should be spraying more fuel than they are so it's causing the trims to be so high.
Does this sound reasonable??

I'm not sure what size injectors the '99 has. I have a set off of a '03 (I think) that I can swap in, but I'm not sure what size they are either lol.
The swap probably isn't necessary on a bolt on 4.8, but they are available.

 

If the pcm was flashed with the stock tune for your truck then I doubt the issue has to do with the injectors. I would be searching for a vacuum leak, even the smallest of leaks will cause your ltft's to be way high.

 

What programer and how specificaly are you disabling your maf? verify your in open loop

 

Using HPtuners. Brought the MAF frequency down to 0. Im going to disconnect it and see if that changes anything

 

Matt,email me your file with some logs.