How does the chip affect your gas mileage? Better/worse?

Honestly I'm not real concerned with maximum performance so much anymore. Got the audi because it has a lot of creature comforts and looks sweet. It's fast enough for what I'll be doing. But if the ECU upgrade saved me a few bucks on premium gas bills that might be something. It'd have to save me a lot of bucks though I suspect--don't these things run about $1k?

 

If you are not concerned about performance then I wouldn't bother with the Chip upgrade. Gas milage will probably not be as good with the chip, but not much worse.