I know I'm posting without pics, but I just got my truck back from the exhaust shop where I had the guy rework the downtubes to use some 2.5" corvette manifolds I got a while back.
There's a noticable "good" difference! I'm not sure if there was an exhaust leak he fixed, or the larger manifolds make that much of a difference, but I have much more noticable torque at low RPMs (1800-2200) which is very nice since that's where the truck seems to end up being on the freeway. I can power through some of the initial hesitation at that range now instead of lugging it like it always did before the change. I could almost see keeping the 4.10's now since it drives so much better, but I'm still going to get the 4.56's in the back in the next week or so. I'm still battling ants in the hardtop.
Before my trip north, I noticed the spark plugs were looking kinda rich and after datalogging it today, I believe that it really is running rich now, which could explain some of my gas mileage problem. Yay, maybe I can get back to 15 mpg again...
The k5 just got a lot more fun to drive!