Well, the first tank of gas (87 octane) returned 18.2 mpg with quite a bit less pinging. Not bad, not bad at all... That was an even mix of highway/city driving. The last tank of gas before the new AFM was 91 octane and returned 16.2 mpg.

The idle issue hasn't completely gone away but it's quite a bit better. I'm still trying to get my hands on a fuel pressure gauge.