I have an 08 Fit sport with AT. Mostly because I am in heavy traffic 3 times a week and manual is a nightmare in those situations.
I feel like I would be very happy with just a bit more power off the line as well as when trying to pass someone on the highway.
What are good things to upgrade first? I know tires are a must so what would you recommend?
20 HP gain would be amazing but from the threads I read, there's no clear parts to get such a gain. Thank you.

 

If it involves getting air to the engine (intake) you can get more power out of replacing it with a short ram intake or a cold air intake. If it involves getting exhaust out of the engine replacing those parts (header, downpipe, b-pipe, axle-back) or even just some can increase power. Just make sure thay the diameters of piping on the exhaust side are equal or you'll create a bottleneck which will reduce power if you go from a larger diameter to a smaller diameter tube. Peruse the forum and you'll surely find more advics of which parts to buy. And don't forget the FlashPro!