yea , i had the same problem on my 97 DX, what I had to do was get the EX headers, they fit...... then use one of my original O2 sensors with an adapter, then had to buy another.... I got an aftermarket universal cat, and it passed smog..... but you will feel much more of a difference when you put the headers on the DX as opposed to EX or Si because those ones already have sort of headers on there and the DX has the cat right by the front restricting it from there......