[RestoCreations]

A couple of points
-You will see a nice hp increase when changing from a restrictive manifold or header to a more free flowing 4 into 4 or long tube header system if you have a high hp engine. If you dont have a high hp engine, you are not going to see much of a change at all. Like was mentioned above, air in and air out. If your cylinder heads, intake, and cam are not up to par, then i would start there.

-I have seen some of these pipes that have a muffler with a flat face and then the flow hole in the center. This causes the air to hit that area like a brick wall. Its a dam, not a bottle neck. In that case, what really needs to be done is to make sure that area has a smooth transition. You can cut the muffler apart and create a smooth transition at that point. However, this requires a lot of work and might not be a project you want to tackle. Im not sure if anybody makes them with a smooth transition or if they just try to compensate the loss caused by the dam by making it smaller with a larger Internal Diameter muffler. I personally prefer the smaller internal diameter mufflers, but only if the hp loss is reasonable. I will take a 20hp flywheel loss any day over hearing loss. Look at the classic chambered website-he has a picture of reducers that make for a smooth transition-that is key. Now if only someone offered an option for 2-1/4 and 2" muffler section that would be nice.
-The louvers do catch the air when turned the correct way and make the pipes quieter/deeper, but you will also get a lot of back popping under deceleration.
-The larger louvers shown above will give a much better and deeper sound when faced the right way. The smaller louvers give the exhaust a higher pitched sound.
-The longer muffler section you can use without making the car look odd, the better.

Dwight-do you still have those inserts or did you toss them?