The mystery of the missing oil?

so, it was less than a quart down? in 6mo and 1K? i wouldn't sweat that in the slightest.

plugs don't look bad, probably the wackiness of the fuel filter/pump/regulator situation in conjunction with the float level in the carb is where the low speed running issue was coming from.

however, this brings up the topic: do you have the correct dipstick for the oil pan and did you add the correct amount of oil at the initial change? i only ask, because most stuff isn't going to give you an oil light if you're less than a quart down.