Thanks for the braindump @GreggPDX - all good advice. Thanks for validating my inclination on the rear seal - that's exactly my worry (that messing with it might induce a problem).

re: SAI and emissions. I'm in CA, and emissions are pretty strictly monitored here. Checking via OBD is the method, and I expect that visual checking is a requirement of the state too. That said, my observations of the emission techs actually performing the visual is hit-and-miss. I suspect that if you drive up with a car that looks modified (think slammed civic with 3inch tips) then you are more than likely going to be subjected to a thorough visual. If, on the other hand, you drive up in a well groomed executive sedan, then you might just get a cursory look over. Perhaps that's just wishful thinking, but I have had recent experiences showing up in 2.7T's with cheaters on the rear 02's (to mask failing cat efficiency codes) and passed with no issues.

I am inclined to remove the SAI plumbing to recover the space (as you suggest) - but I am still not decided on what to do with the downpipes/exhaust. One thought is to put away the stock downpipes (hanging on to them in case I need to restore stock hardware for emission compliance at a later date) and to use some thing like these in their place - while retaining stock exhaust downstream.

re: recessed manifold fasteners: So, they are 12mm? And you managed to find a thin-wall socket to fit? I just had two thin-wall alternatives arrive today from AMZN - and neither fit. What brand do you have?

And, no, I do not have the Elsa-win manuals. Off searching now.

BTW: Stephen Kendrish introduced me to a tuner - Alex - of whom, I began an email dialogue with a couple of months back (and with me promising to be back in touch when I got nearer to completing the conversion). Wondering if nubcake and Alex are one and the same?