I won't be able to rip the thing apart again until this afternoon, but I just got access to the 300 degree forum and someone just posted basically the same problem I seem to be having, and it was their lower injector seals. All things considered I feel very confident that's my problem. Hopefully I'm right and will have this whooped today or tomorrow.
Thanks again for the idea. I had assumed (!!!) they were seated correctly since it seemed like they "must be", but upon closer inspection/more thought, I can see how they might not be.