What basic mods should I make for my lancer 09, to increase Hp?

You also have to think about voiding your warranty as well. Even the K&N air filter can void your warranty, because if they find something wrong with the engine. They will blame the K&N filter because its letting more dirt in with more air flow. Then your warranty is voided. It has happened to couple of people already. Plus finding cheap stuff isn't going to increase your horsepower and you won't notice a difference. Maybe 5-6 bHP thats it though.

But anyways, for "cheaper" material aftermarkets. I would stick with the K&N air filter and the loud Tsudo exhaust. You can only choose an air filter or the intake. You can't choose both. Or else you'll be wasting money instead. The others are more expensive parts like the reflash ecu is going to cost you $500, headers are $500, and full headerback exhaust is going to cost you $800. But with just these three you can get an easy 20-25 at the wheels. But they are more legimate than the "cheap" stuff your going to get though.

I have an 08 lancer, I just got a front splitter to help make it more aerodynamic ($150- you can find it cheaper on craigslist or roadracemotorsports.com) I have a road race motor sports short ram intake ($200 www.roadracemotorsports.com). You can also buy an HKS universal muffler (craigslist) then go get an exhaust made at an exhaust shop. Its true that the engine mods would void your warranty but these simple mods are removable. Just make sure to put the stock stuff back on if something goes wrong.

Weight reduction and things like that can also be used to improve your horse power, if you surf craigslist and other car forums, you can find cheap racing seats, lighter rims and higher quality tires.

An exhaust on any car is a waste of time (and money) unless it has a very high performance engine set up. I would recommend trying playing with the computer (with the right software of course). EcuTek has new software for lancer out now ₤215

there's other little things that you could help with the performance of the car like better handling and response. there is a pully from roadrace motorsports that increases throttle response. there's also a short shifter from works. the car is still too new to have so many mods for it out. if you don't mind spending up to 5k then there is the turbo from roadrace. i recommend you join our forum so you could learn more about each performance/suspension parts just so you could come up with a decision for this beauty.

get you ECU remaped at an tuning company

amsperformace.com