vacuum advance

It's a 400 bored .040 over, fairly mild cam (comp xe cam 224/230 lift at 050 inch lift with 477/480 lift) 750 cfm holley, did change secondary spring, main jets, and power valve. I reused the gaskets. Should I have put a new gasket behind the metering block? Also shaved heads and weiand dual plane intake. Idles around 1000 in park and 500 in drive. If It is not supposed to pull vacuum at idle, do you really need to disconnect it when setting your initial timing?