I have an '05 Civic Sedan EX SE (Auto), I'm wondering what are some good start-off things I can do to improve performance.

 

It's funny that most of these questions get posted in the I/H/E section. Just posting it here means you have a good idea of where to start. I went in this order:

1. Short ram intake with K&N filter. Cold air intake is also an option. AEM makes the best of both, but check out K&N too.
2. Cat-back exhaust. Popular opinion will tell you GReddy Evo, but shop around, these can get pretty expensive. I have a Holley cat-back and I am pleased with it.
3. Header. I got a DC, but I hear Greddy makes a good one too. The quality of your header is important so make sure you don't get a cheap one only to be disappointed.

I think you will find that most people started with some combination of these 3. Don't expect 50 Hp from these but it will certainly punch up your performance.

 

Yeah, I've heard that many people start with intakes. Do you know anything about the V2 Intake by AEM? Seems to be new and I've read good things about it.

By K&N Filter, that's an air filter, right? (I'm not too familiar with brands, but I'll look it up.)

What's a "Cat-back" exhaust? [:@] I'm new at this stuff.

 

All I know about AEM is that it's supposed to be the bomb-diggity. Do a search for it on here and read through some of the old posts, including short ram vs. cold air. K&N is the world's best air filter and they are making short rams now too. AEM actually uses K&N filters for their intakes. Click on their link in here to check for applications. They have dyno sheets in there too to see what kind of Hp you can expect to get. At AEM's website they have a little sound clip where you can hear the difference between stock and the V2, they also have dyno sheets.

A cat-back system is all of the piping from, but not including, the catalytic converter to the exhaust tip. The pipes are bigger, usually 2.25" and mandrel bent to allow for much improved exhaust flow. Read this: Backpressure Myth

 

Alrightey, I've been looking around and I want to confirm a few things.

K&N Air Filter - Is this the right thing?
AEM V2 Intake - Looks like a good intake. Eh, like you said, it's AEM.
Greddy EVO 2 Exhaust System - Wow... expensive.
DC Sports Header 4-2-1 - No idea what 4-2-1 means, but... damn, expensive, too!

From what I understand, 2001-200[3/4] parts work with 2005 as far as the engine stuff goes, correct? (At least on the EX.)

Edit: Whoops, a mistake on the Header link.

 

The K&N you have there is just the stock replacement. It will give you some power gain and better gas mileage but you want a short ram intake like this: Air Charger. You won't see much difference between the K&N and the AEM performance-wise according to their respective dynos.

GReddy or DC anything is going to be expensive, but they can charge those prices because they are the best. I hear good things about Tsuedo(sp?) stuff and it's half the price of those two (I forget who makes Tsuedo, but it's a reputable company). Like I said, shop around and ask questions on here. Do searches for anything you are curious about. If you don't mind picking up used stuff, second hand could save you a bundle. Check the classifieds on here and look around on e-bay constantly.

A 4-2-1 header is a header with 4 pipes (runners) into 2 and then into 1 big collector that goes into your catalytic converter. A 4-1 means all 4 runners go directly into the collector. It's generally accepted that 4-2-1 is better for low-end/mid-range power (daily driving) and 4-1 is better at the top end of the powerband.

You might want to check on fitment for the 7th generation ('01+) stuff because I have a 5th gen, but I am pretty sure the parts are interchangeable.

 

WAY impressed with the V2. great low end increases...i love it...and it sounds like, well it sounds like a herd of angry elephants coming you're way! def. recommend!