Another $1k later, and Tundra finally runs like it should.
Initially bought the $500 Gen 2 bypass kit from Hewitt Technologies. Pretty easy install, took all of 30 mins. Was fine for less than 48hrs, and then limp mode came back.
Unfortunately it wouldn't "talk" the same language with the aftermarket SAI valves that were installed. So spent another $500 on 2 pressure sensors from Hewitt. Now all works like it should.
For now left the (now inactive) valves on there, but eventually will remove that whole SAI system. Weight reduction lol.