[scottsee]

or you can replace the air box with an adaptor and cheap $10 air filter..

cat backs dont fit to the headers. they mount to the cat. hence the term cat-back. if you plan on upgrading your DP you might run into some problems with specific vendors. Apexi dp's and evo3 o2 housing dont like each other for example.

i would answer your question better but i dont know what kind of car you have. read the rules of this fourm in the stickys and add the correct information in your signiture box so we all know what we need to too answer your questions.