Orphan72

So I get the infamous 0440 when they read my car. I chase it all down in past threads and basically I came up with: There is no telling what it could be.
I got a new gas cap, checked the EGR tube, new fuel filter, looked at the fuel pump, factory header (for the moment), and aftermarket exhaust. The exhaust was put on about 100k miles ago, and since I live in Kentucky (for the moment), I do not have a smog check or anything like that. I bought my car in Tennessee back in '99.
If everything is correct, this will not cause any other problems, right?
I don't want to take it to the dealership around here, but if it absolutely, positively, necessary I guess I could.