Problem with the catalytic substrate is, it raises the exhaust temperature, sometimes so much, it will cause the outer shroud to melt which is what happens on the Echo CS top handle saws. There are numerous customer complaints on the net about that. Removal of the cat on them eliminates the issue. Even complaints on the Echo manufacturers website. Just like you car with a catalytic converter. That to increases the exhaust temperature and really increases it if your fuel trim is wonky. Why car manufacturers caution about parking over dry grass. The cat will set it in fire. Same applies to a saw with a catalytic converter.
Instead of fiddling with the muffler on my Echo CS, I bought an aftermarket muffler (Forrester) but I found out later that Echo also offers a non cat muffler in the website as a replacement, or at least did a year ago.. 23 bucks was an easy solution and I tossed the cat one in the scrap metal bin.
The heat level the cat raises the exhaust temp to, entirely depends on the fuel to air ratio, so if you set the saw to run rich, the cat will raise the temp of the exhaust more. One reason why there are limiter caps in new saws.
With Echo, only the 'homeowner' saws have cat's. The 'professional' saws don't, or at leas they didn't. That may have changed. I know my CS590 don't as I have removed and modified it for easier breathing.
