So let me start by saying that I am very novice when it comes to mechanical practices, but I have a 2004 Civic that overheated and ruined my 116,xxx mile stock engine. With the amount of head gasket replacement and not knowing the damage to possible warped internals I opted to replace it with a 50k mile JDM.
I had my mechanically inclined buddy help me install it in the driveway. Everything seemed like it went well and I took it to a shop to verify that everything seemed kosher with the new install.
However, the car sounds like a damn go kart and the shop said I have a clogged catalytic converter which is probably what overheated my first engine. If this is the case, I do not live in an emissions controlled state and so what reasonable and inexpensive option do I have to not spend much more than I already have on this problem? Thanks guys.

 

Buy an inexpensive aftermarket cat. Bolts in, meets federal laws, won't stink, and no error codes.

 

Thank you. Appreciate the response.