Reply to "Why are 180 headers illegal in CA?"

They are not mass produced. They are made like any other headers, by human hand, built on a buck.

One thing that needs to be understood with these things is that if you are building them in one piece, they are only going to fit closely the engine that they are being built on. Secondly, they are going to give you fits getting them on in one piece. In fact, once you run them and they take a set, just getting them off is going to be not easy and at least a two man job. Forget about getting them back on.

You are at least going to have to remove the rear deck and you definitely are going to scratch everything up.

The header flanges on the one piece designs are angled 45 degrees the wrong way for ease of removal or installation.

Building them in one piece is going to encourage them to warp in virtually every axis.

Mine are flanged in the middle. They've been on and off dozens of times. They fit like a glove in the beginning and they still do now.
The flanging makes the entire set kick down easily and makes it very easy to remove any single component without removing the entire set.
NO slip tubes on mine. Everything bolts together with 1/2" flanges.

Design wise, keeping the left side separate from the right reduces the tendency of them to warp. Does it look as nice as them all built in a one piece squirrel cage? No, but serviceability to me is very important.

All of the header bolt holes line up perfectly and there is no twisting or warping of the flanges anywhere.

Exactly what other criteria everyone else is setting for them is beyond me but I suppose ease of satisfaction is a personal thing?