Hey:
First, I'd just stick with Holley if possible. I know Demon is just back from bankruptcy and all that, but before bankruptcy there were all kinds of problems with Demon carbs. If you do go demon, make sure you take it apart before you install. Make sure everything is as it should be and blow the aluminum shavings out.
Second, the metering plate and bowl gaskets are the same as holley. Squirters, power valves are the same. Fuel line is different.
The Idle thing is a gimmick unless you're running a gigantic camshaft.
What is your combo? What is the intended purpose? Street/strip? Race?
