Going off my wideband they were fine (which I'm sure Brett is referring to in his post). The old wreck Sard 800's were 10 times more grumpy than the ID2000's are.
With the old wrecks of injectors (Sards, Rochester, whatever else) that was an issue. Today with the ID/Bosch 14V's for example, it's not really an issue.
Look at that. ID 2000's on a pissy 1.8 NA.
Have you tried another gauge? Maybe that one just reads low?
I agree with Johnny. If it's still running well just keep flogging it. A stock replacement engine is cheap enough.
You're buying pistons and rods, (and in your case another 2.6 L crank, then paying for it to be screwed together anyway. What's a little more for a bigger crank? It really is a no brainer.
Have you considered something like a GTX 63 or 67 mm machined into stock style housings? It's been done before and will give a much better result. There have been a few guys that have done that on here.