Randy, I saw that same ridge on the top of the exhaust port in the EQ saws I got. I'm not sure what it's supposed to do: it allows a small portion of the exhaust port to open about 5 degrees before the entire port lip gets exposed. I used it as a guide when I was raising the exhaust port up to compensate for removing the base gasket.
Also, these saws just have a single ring piston and the pin is on the intake side, so you can make the exhaust port as wide as the metal allows.
Also, these saws just have a single ring piston and the pin is on the intake side, so you can make the exhaust port as wide as the metal allows.