Audacious Epigone presents data showing Episcopalians average higher IQs than Jews while earning much less. Jews apparently earn much more than their IQs would predict, while Episcopalians earn less.
Looking at GSS data from 1996-2006, it appears only 52/132 = 39.4% of Episcopalians report "England & Wales" ancestry, only around 3/4 of those raised Episcopalian remain Episcopalian, and only around 2/3 of Episcopalians were raised Episcopalian. In other words, Episcopalians don't represent some sort of separate, endogamous breeding group, but merely a self-selecting subset of white Americans. For example, the GSS dataset shows 7 individuals with average 7.43 wordsum who were raised Southern Baptist and are now Episcopalian, and 5 individuals with average wordsum of 5.75 who were raised Episcopalian and are now Southern Baptist.
Update: Inductivist links to this analysis of NLSY data showing that at any given level of IQ White Males earn less than male Jews.