I have the same setup - 5.0L, AOD, and have the 3.55 axle. See the same thing you do - around 65, just seems to lose its oomph. Keeping it out of O/D helps somewhat - but concerned about flogging the tired horses any more than I have to.[/quote]

yea mine is 3.55 , its amazing it still had the tag on the diff. when i got it, and at least i'm not the only one with this problem

 

ive heard nothing but bad things when it comes to messing with the egr, plus unpluging it will make it idle like crap from what i have heard

 

I have this same problem, I just got the truck and don't even know what axle I have, but mine's a '93 with the I6. I changed plugs and fuel filter, but haven't checked codes yet or the egr. I'm guessing with how my truck looks it could easily be anything that would have been prevented with regular maintenance.

 

I have no problem with my idle with that pesky EGR valve turned off. In fact I ran a whole lot better with it off. Mine is all clogged up too.

 

did you just unplug it?

 

I unplugged it and accidentally broke the air lines going to it. You get a CEL but I was getting those any ways. Or you can buy/make a plate to block off the place it goes into the pipes, and then make a resistor for the sensor to get rid of the CEL.