Tuning woes persist, working my way through the list of possible causes but have not found anything touch the 3-3100k headache spot. I let it run lean in that range and pulled the plugs but there's nothing really jumping out or pointing me in any specific direction.
Although, I think I made a really worthwhile change with the injectors and also think it's a worthwhile piece of information to put out for anyone running a Nathan intake with ID injectors or just no injector clips in general - you probably have an air leak around the base of your injectors. Here is a picture of where the injector sat with no clip after being forced down into the manifold by fuel pressure:
The problem is that the injector bung is slash cut into the runner, and at this height the bottom o-ring is hitting the high edge of the cut. This was preventing a good seal and causing an air leak under boost. I bought a new set of adapters that allowed me to use clips (thanks again Tom, saved me some homework on that one) and you can see how the injectors are pulled higher up into the rail now:
This holds the injector up in the bung and allows for a proper seal. I was kind of hoping I'd jump in the car and find it was overly rich at 3k now but no change in that range. The only difference I've noticed is that it's now reluctant to start and idling rough. I haven't changed the tune at all, so not sure if eliminating the leak around the injectors would affect that portion of the tables or not. Going to log it and see if Doc Howard can help me out at all.
Interesting to find that the ID adapters have some kind of insert in the top. It's almost like a diffuser, open on either side. The new adapters are just an open hole. Anyone know why ID would have something like this in the adapter?
I'm going to swap coils tonight from my Dad's ls7 and eliminate my coils as the source of an odd rpm-specific misfire. After that I'm getting thin on ideas for what's going on. I will probably end up sending the injectors out, but it's $100+probably two weeks of having the car down which is a real bummer for a hail mary pass.
Beyond that I'm kind of stuck looking at my wiring harness, though I'm hard pressed to think of a wiring issue that would be rpm specific like this. At some point, barring any welcome mechanical cause presenting itself, I'm back to square 1 and this being some kind of odd tuning issue that is just really hard to walk in. I wonder if maybe I could get a guy like Kenny actually in the car if it could be worked out in a few hours, but I just don't have the depth of knowledge for this puzzle from a tuning standpoint. I would feel a little better about the system if I could work out the 5k plus range, so maybe I'll have to sack up and start getting up top to see if it can be wrangled.
We've kicked around the idea of putting the stock intake on to see what difference it makes, thinking of changes from the year 1 setup when this first arose, which would be feasible but I have no real way to get a fuel rail on it now that I have the -6 lines. I used to have a Nathan fuel rail for a stock manifold but have sold it on, anyone want to rent one out?
. Dare I admit I've grown used to the bit of color? 
