Who guards the guardians? “Self Certification?”
I've been staying out of this one for the most part - I'm not a pilot, and my expertise is Propulsion, not Flight Controls.
But "Self Certification" is a serious miss-representation of the process. Boeing is "Delegated", not self certifying. The FAA is intimately involved in the a new Amended Type Certificate (ATC) (which is the case for the MAX). I was a DER or the delegated equivalent AR for nearly 30 years and was quite involved in the certification process.
A new ATC is a long, complicated process, with countless meetings between Boeing and the FAA. There would be a high level 'Tech Fam' where Boeing described
all the changes planned for the MAX relative to the NG, then a series of specialist meetings where the certification basis is negotiated (this somewhat unique for an ATC (rather than a new TC) and gets into something called the Change Product Rule or CPR - CPR basically says any system that's changed as part of the new ATC has to step up to the latest regulations and be re-certified, but there are exceptions and these are what get negotiated). Then there would be another set of specialists meetings where the planned changes are discussed in detail, and the FAA would determine which items will be FAA retained and what will be delegated. In the Propulsion world, precious few changes got delegated - although many of the documenting deliverables were delegated (in my case, the FAA would routinely delegated the flight test reports, since the FAA would nearly always participate in the flight test and the 'report' was simply my documentation of what they'd already witnessed).
I don't know what happened with MCAS - I'd be somewhat surprised if MCAS was fully delegated but it's certainly possible - but to say the FAA was unaware or uninvolved in the certification of MCAS doesn't reflect the way Boeing and the FAA work.