Welcome aboard.
B16s are few and far between on this board, but your mileage is impressive. I used to own a 98 Integra GSR and I could eek out 42MPG with it too, so there is something in the ECU program that allows us to squeak some mileage out.
Frankly, I'm surprised that going to a larger diameter header netted you more mileage. what did you upgrade from, the stock B16 header?
Your car would be a perfect candidate for a D15Z1 swap, then you could pull off 60MPG
