Improve performance of 2013 Civic si?

Just trade it in for a faster sporty car.

Aftermarket parts will always effect warranty, it's a risk you take. As long as the technician can prove your added on parts caused the failure they can deny you a repair so long as the effected OEM part is related to the aftermarket part. Once again proof is needed, they can't just deny you repair work on a faulty crankshaft bearing because you have an intake. With that, research the Magnuson Moss Warranty Act.

You're not gonna get anything that will make a world of difference for less than $3k that won't effect your warranty. You could do an Intake/Header/Cat-back Exhaust setup to get a little more power and by the time that's all done (if you do it right and buy reliable parts) you'll be nearing the $3k.

If you want instant noticeable gains you can research turbo kits in your price range and have the car tuned, but forced induction and ECU tuning will void warranty.

2013 Civic Si Aftermarket Parts

First any engine modification will void the warranty. Period! Secondly, with under $3K and in real life situation, there is nothing you can add to the vehicle to have more ..umph without keep adding more needed items to make it right.

Just remember the void warranty: It'll cost more than $3K in a long run.. in my opinion..

You've got about 200 hp, but it's pretty peaky, right? That's kind of the curse of the small, naturally-aspirated 4 cylinder. All your power is north of 5,000 rpm. I'd go to a real Civic forum and ask those boys if there's anything to offer low-end grunt where you need it.

I wouldnt mess around with mods for that car. you wont gain much power or performance and you certainly will void your warranty.

Go for form, coilovers and nice set of wheels.

What Landon said.