I just put on a header and full greddy Evo 2 exhaust on the car, when at high rpms and im letting the rpms slow me down im getting small pops from the exhaust, something wrong?

 

nope, likely the stock exhaust you had on there was doing a good job of killing the noise (the muffler and resonater especially). Now that you have a better-flowing exhaust thats set more for performance then for comfort, you'll hear stuff like that more.

 

you may have a very small leak somewhere, but if they are just very small pops, then thats probably normal.

 

I didn't know these mentioned Civics had carburetors. [8D]

Any time you change your exhaust the muffler is going to have a significantly different back pressure and flow than the stock one and you will hear a lot more noises.

If you are in 4th gear say and put your foot to the floor, if you don't hear any leaks you are probably all right.