I have an 07 crew cab with the 4.0L. I want to install the OBX short headers and tie then into the pre-cats like the stock manifold. I'm good with fabrication and have my own tig welder so that should not be a problem. are the stock pre-cats very restrictive? I don't even plan on putting a performance exhaust on the truck. I just noticed what a poor manifold design the truck had and know adding short headers would be a huge improvment. I'm not looking for huge power gains but just simply want to correct an obvious fault.
now i will consider upgrading the whole exhaust if it is comparible to the stock exhaust while riding in the cabin. Are the performance gains worth the money?
My real goal is to improve my MPG by making the engine more efficient and add some lower end pickup too. I do a lot of Highway driving.