Engine sounds good Cat... that wet hollow plop, plop sound at idle is the valve over lap, when the valves open there is pressure released across the exhaust / intake... like putting your finger in your mouth and quickly popping your finger out one side, you get that wet pop sound.... it happens when the exhaust pressure pops back across the intake... when the exhaust gas flow velocity increases, scavenging pulls fresh fuel across the overlap from the intake, and you get a pressure wave that bounces back and forth across the overlap, and you hear that plop, plop, plopplop plop. sound in the exhaust headers.

In regards to the ignition timing reverting to the "base timing" full advance below 1000rpm, I have not experienced that with CH ign... there is a start rpm argument that initiates spark between 150-200 rpm for startup, and once the engine is running, its on the ign map curve... I know with the early rcxel ign sys you can turn the engine over very slowly, and you will get a spark to occur.