On a dual exhaust system there is a pipe called an H pipe. It is the pipe in between the dual pipes that keeps them in place for one thing. It also equalizes the pulses of the exhausts and lets them communicate equally with both sides of the engine. This will also give you more torque in the low to middle rpm ranges. It will give a more mellow tone to the exhaust and help prevent the back bubbling when the engine backs off. The best thing is to buy a kit that has all that you need.
Step 1 - Getting the Car Ready
Start by jacking up the front of the car with the jack put the jack stands underneath the frame of the car on the front. The more head room you have under there the easier it will be to work. Now remove the old exhaust. We are going to install a an adapter kit to have your H pipe in the exhaust.
Step 2 - Removing the Old Exhaust
Unbolt the the muffler system and remove all the hangers that are holding it in place. Cut the tail pipe in half as it goes over the axle, this is the easiest way to remove the pipe if it is stock. Remove from the rubber hangers and keep them on the car.
Step 3 - Getting the Pipes Ready for Cutting
Following the instructions You need to cut the H pipe so that the adapters will fit over it and the two pipes that are made from the cut pipes. They will tell you to cut the pipe on the inside after measuring 2 inches from the weld between the Y pipe and the catalytic converter. Make sure you mark it correctly and if possible cut just a little less , you can always cut more off if you need. If you cut too much you are going to need an adapter.
Step 4 - Cutting and Installing the H
After marking carefully start the cut using the cutting tool. Cut slowly and carefully. Always wear eye protection doing these jobs.Just take your time and do it right. After you have cut the pipes to the dimensions required, the adapter pipe should just slide on. Now do the other side. You will notice that one side of the pipe flange is longer than the other. This side goes on the drivers side. After the H pipe is fixed to the pipes on the car, slide the bolts back on. The U bolt that is larger goes on either side and the small one is for the center crossover where the two halves of the adapter connect. Don't tighten them yet, just finger tighten them on.
Step 5 - Putting it Back Together
Now looking on the drivers side, locate the brake line. There is a brake shield in the kit that will go over this and keep it protected from the exhaust. Install this according to instructions. Now you are ready to put the exhaust back into place. Make sure you use all the mounting items included in the kit. Reuse the rubber hangers in the back of the exhaust and use the new ones where you placed the H at. Now go back and tighten up all the hangers and U bolts after you have made any adjustments necessary. Start the car and test for leaks.