I called magnaflow today and asked about cat back systems for the 2004's. They said that they should have a kit out in several months. Then they asked me where I was calling from (Maryland) because they were looking for someone with a 2004 near there headquarters in California that would let them take measurments of their truck so they could starts designing. It might be worth a free exhaust system or something and also get things rolling on a kit for the rest of us.

 

Where are they at in California?

 

I'm not sure but there is a contact number on their website.