So I went to take my civic for some servicing, new spark plugs and what-not, also to see if they could fix an issue I have when shifting. Basically, sometimes when I shift to the next gear, it will continue to rev up, and then a couple seconds after I've put it in gear, it will rev down to where it should be.

The mechanic thought it may have to do with some clutch timing, but that didn't end up being the issue, and the only thought he had as to what it may be is an aftermarket Injen Tech air intake that was installed in the car before I bought it.

Could this be the issue? If so, would an OEM intake fix it? If not, what are some ideas of what this could be?

Thank you

That doesn't sound like an intake issue to me. So you have manual transmission, right? Have you ever changed the clutch and transmission fluids? That definitely wouldn't hurt anything.

It is a 6 speed manual, also the clutch is about a month new. Could it have been an installation issue?

I guess it's possible... What year/trim/body style do you have? What kind of clutch did you get? I'm not so good with transmissions but did you have the same issue before the new clutch?

This is a 2007 civic si coupe 2.0L. I have no idea what the clutch was before, nor do I know if it is oem or aftermarket. I got this car after it was already installed.

I was driving around today and noticed it may not have anything to do with shifting. It seems to happen when I accelerate. It'll rev up then catch and start going. It only happens periodically, it's not constant.

Compare to an identical car if possible.