Power problem.

A while back (summer/fall) I installed an exhaust header on my 93 civic ex. I noticed that sometimes it would lack power when I pressed on the gas. Recently with the colder weather I notice that it runs a little better and is a little more responsive. Im trying to figure out why this happens and what I can do so that I can get better performance out of it. Any suggestions?

When air is colder, the air molecules compact more together (the air is more dense). The colder and more dense the air, the better it is for your engine. That's basically why people use those "ice box" things (aluminum boxes that house the filter of a short ram intake). It prevents a lot of the heat from the engine bay from heating up the air going into your intake (which goes into the engine), and gives you better performance. Also in some areas on the US, gas that is sold in the winter is made to burn easier and cleaner (I know NY does this). So that might have a little bit to do with it as well.

Otherwise you might want to think about doing a tune up to help (new plugs, plug wires, use a different oil for the winter months, replace the intake filter, fuel filter, etc).

I was thinking of doin a tune up since I havent done that in a while. Thanks. Do you think I should go as far as getting cold air intake? I have short ram intake now.

If the headers are allowing greater exhaust escape, it is possible that your back pressure is being effected. If there is reduced back pressure, this is often accompanied by reduced low rpm power exchanged for a high rpm advantage. More air provided by an intake cold or otherwise could possibly make the difference. Underdrive pulleys could possibly increase your power but there's less energy supplied to the alternater, ac, and power steering.But start with a tune up.