05 V8 Limited - Motor Replacement, What Else?

[AngleAway]

Hey all, my daughter has a 2005 Limited (vvti) V8, with ~360k miles that recently blew the head gasket. I sourced a replacement used motor, and am planning to take a hard look at the exhaust manifold/exhaust system while we have the motor out.

Prior to this issue, we had several instances of faulty catalytic converter codes being thrown. A couple of places looked at it and said it needed new cat's. So this leads me down the path of potentially replacing everything from the manifold back.

I'm considering the long tube doug thorley headers, Y-pipe, and URD cat back exhaust. As I understand it, it is possible to make this install and not have CEL issues with some creative approaches.

I'm working with a local mechanic that is a former Toyota certified tech, with 20+ years of experience, so I feel like I'm in good hands.

Question is : am I on a good track? Should I look at replacing/upgrading other systems while I have the motor out?

Any recommendations for a different exhaust setup? I'm concerned that going with the shorty DT headers may be problematic due to the previous cat error codes. Is that founded or am I making more of a problem than truly exists?

I don't care much about performance increase, but the way I see it if I am going to spend a ton on the manifold/exhaust anyway, I should get a gain from it.

 

[Keros]

I have shorties and a custom system, with magnaflow cats. The tech put some spacers on the O2 sensors during install and I never had a CEL related to the 02/cats. You'll probably want to do the air injection system bypass while you're at it and save yourself a headache down the road.

I've no experience about the long tubes other than what others have posted. I acquired my shorties before the long tubes were available... otherwise I probably would have taken the dive on it, but that's probably because I like creating unnecessary problems...