1. The Borla header and exhaust kit comes complete with all necessary hardware to complete the install. Two exhaust gaskets are included with the header because two different heads were used on 4.0L engines. The only parts you'll have to reuse during the install is your vehicle's oxygen sensor and catalytic converter.
If you own a 4.0L-powered Jeep, you've either had the exhaust manifold crack, or you're about to. Design flaws in the manifold almost guarantee failure at some point. One of our project Wranglers blew out its manifold at just 48,000 miles, so we were faced with having to fix it just like everyone else. We turned to Borla Performance Industries, because it offers a top-notch header for the 4.0L engine, and because of Borla's excellent reputation for fit and finish, ease of installation and long life. Borla's header kit includes a high-flow header constructed of T-304 stainless steel, and it also includes a new gasket and all hardware to complete the install. Clearly it seemed only natural to install Borla's complete free-flowing Wrangler exhaust as well. The exhaust system includes stainless steel pipes, a muffler, chrome tip and all of the necessary hardware to complete the job.
We shot photos and jotted notes as Matt Dinelli of Attitude Performance installed the complete system in about two hours. Your install time may vary, depending on your tool selection and overall mechanical experience. Overall, the kit's quality and ease-of-install were very impressive, but if we had to nit-pick, we'd target the new header crossover pipe, which travels under the transmission and decreases ground clearance by approximately 2 inches.
Even if you haven't blown out your 4.0's stock manifold or exhaust yet, a Borla system is a beneficial upgrade that will offer increased performance and a pleasant exhaust tone with no aggravating cabin reverberations. Don't own a Jeep? Borla makes exhaust systems and headers for a number of other makes and models.
2. Once the intake manifold is removed, you can remove the stock exhaust manifold. After removal, make sure you clean the surface where the new gasket will mate against the block. | 
3. Matt Dinelli at Attitude Performance prefers to install studs into the block to facilitate easy reassembly of the new header and stock intake. Slide the new Borla header over the studs. | 
4. Reinstall the stock intake manifold. There are dowel pins on the block to facilitate alignment of the intake to the head. Reattach all of the mounting bolts and nuts, power-steering pump, fuel line, throttle cable, and so on. |
5. To install the exhaust system, remove all of the factory system except for the catalytic converter. You'll need to cut the stock exhaust pipe 21/2 inches in front of the front catalytic converter hanger. Install the new pipe that connects the Borla header to the catalytic converter using the supplied hardware. | 
6. Install the rest of the Borla exhaust following the included instructions. It's easy, and the system uses the stock hangers. Attach all of the components but don't tighten until you're sure that there's no contact with any underbody area. Once this is confirmed, tighten all of the clamps. | |