All I can say is make sure you have the gap right.
When I got mine, turbo, but I saw this,
Not sure if you can read it, but the sticker in the engine well states a .50 gap.
And I got 12 mpg for a couple days. I found on another forum that most are running a 35 or 32 gap. I pulled mine, regapped to .35 and am getting about 23-24 mpg. Turbo lite auto. So I would guess the stick should get close to thirty.