Be careful with upgrading the turbo. If you go too big, the lag will make the truck less responsive down low (especially with stock tuning), and it will feel (and probably be) slower. With a properly sized upgraded drop in, you can prevent the losses on the bottom end and you might pick up a tiny bit of power overall just because of the increased efficiency of the better turbo. It won't be a noticeable difference unless you have very highly sensitive butt-dyno.
As for the actual problem, without knowing the exact code, we are just guessing here. If it was a circuit code, it's likely a wiring issue or failing sensor, but if it's anything else, it could be a mechanical issue with the vanes. I don't see a lot of vane sticking problems, but it does happen from time to time. I've never had much luck with trying to clean the vanes and getting things working like they should, and as much work as it is to pull a turbo on an LBZ, I'm not sure it's worth the gamble.
