[DanEC]

That's not a big duration cam so I wouldn't think you would need to adjust the primary and secondary throttle plate curb idle positions to keep good idle response and for it to shut off when the key is killed. When you adjust the idle mixtures do you get a rich and lean roll off of idle speed or is it unresponsive to idle mixture adjustment? An idle of 900 is not particularly high either. So, you might experiment a little with timing and different fuel.