The main difficulty in installing headers, particularly on a 4x4, is the lack of clearance to remove the manifold heat shields and remove/install manifolds/headers.ĬAUTION: The steering shaft on the driver's side gets unbolted for clearance purposes. Because of reason (1) I don't like the idea of cutting off 2004 primary cats and welding them onto the end of short tubes. You want to avoid two common problems (1) allowing the oem primary cats to disintegrate and wipe out the engine due to back sucked cat grit and (2) allowing the oem exhaust pipe to rust off and melt the rear wiring harness. You can get a JBA cat back with a decent Y-pipe for around $350 (which is one of the lower cost catbacks), of course there are numerous different cat-back/muffler choices. The 04 exhaust has a horrible crushed y-pipe. To correct the AFR after header install, most people run Uprev. Berk makes bolt-up B-pipes with cats and bungs, or you could buy some appropriate sized high flow cats and have the B-pipes with cats welded up. To avoid throwing codes, you need adequate cats in the B-pipes with the aft sensor bungs mounted downstream of the cats or on the aft end of the cats.

The oem exhaust on an 04 4wd also has secondary cats in the b-pipes and another set of sensors. The forward sensors go in the bungs provided in the headers. Click to expand.The long tubes replace oem manifolds & integrated primary cats and bolt up to the factory B-pipes, no cutting required.

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