All I have is a K&N drop in filter, custom tune, and 2 Optima red top batteries, yellow tops are good if you're going to drain them down, but not worth the extra $$ if you're not.
I won't put any extra performance mods in my Hoe because, well I enjoy not having to worry about something f'ing up!!! I did the tune so I could get longer 4cylinder mode, extra trq for when I'm towing my boat, and overall better gas mileage.
If you want to add performance mods, save up and buy another car for that reason, to mod. I have daily driven heavily modded cars/trucks and it gets old very quickly always having something break and needing a ride for weeks or months, case in point, I just blew the built Ram clutch in my Z06 (there's another $1,300)
If you're going to do exhaust stay away from Crapmaster!!! They are only good for 5.0 Mustangs