what the first engine/exaust mods should I do? Options

[Speedy_Gonzales]

and where is the best place to buy parts?

[mgnt232]

The intakes are cheapest on ebay, and they well fit, no need to go through a bunch of different angled pieces and couplers, it will all be together already. I bought my CAI off ebay (i extended mine) but its sounds good at any rmp above 1k. As soon as I hit the gas a little you can hear it, and obviously the more you hit on it the louder it gets

And make sure if you are getting a catback that some exhaust shop will bend the piping! no one does it within a 60 mile radius of me! make sure they can first!... I got a magnaflow res and muffler, and its a deep sound but all exhaust systems end up a little raspier, after you add a header. Increasing the flow and eliminating the pre-cat.

And with a header (at least with my ST) as long as you have the first o2 sensor in, the second can just dangle with no CEL, or noticeable difference in driving

ohh...and search

[HectortheRican]

And with a header (at least with my ST) as long as you have the first o2 sensor in, the second can just dangle with no CEL, or noticeable difference in driving

Bad idea. It could get smashed for whatever reason and that'll throw the CEL since the O2 sensor is actually not reading ANYTHING. Just tell the exhaust shop to cut off the bung from the old manifold, cut a hole in the new header and weld it on. It'll be 20 extra bucks, 30 tops.