First, you should NOT be using the Sec. 911 FEIE (Foreign Earned Income Exclusion) if you want to invest in an IRA:
Second, okay assuming that you are able to invest in an IRA:
The post is referenced in he above tweet was written by Chad and Peggy Creveling and appeared in the Wall Street Journal on August 23, 2016. It is well written and very interesting. You will find some of their blog posts here. The post will NOT be of interest to “accidental Americans’ and other “long term” Americans abroad. The reason is simple. The rules are so complicated that only short term – “Homelanders Abroad” would undetake the compliance burden.
Nevertheless, I recommend the article to you. It will reinforce the impossibility of navigating U.S. tax rules if you live outside the United States.
Citizenship Taxation - Theory vs. Reality 