I think you are way ahead of the game in terms of hp. So, if you want more, you really need to think about your goals and your budget! You could spend $2800 on downpipes and exhaust for another 25 or so HP. After that you're talking about turbos, and that's where it gets interesting. It's my personal opinion that modifying the stock turbos is not only expensive, but because of the stock housing limitations, they just aren't worth it. So then it's aftermarket turbos, and if you take that approach, all of budget spent on downpipes and exhaust might have to be scrapped or at least reworked/fabbed.