Pan vacuum tech
 

I'm trying to build more pan vacuum pre run. I run an analog gauge in the car and can get it to 4" fairly easy, before a run. When I pull a vacuum on the engine without the car running, with an electric pump, I can get it to almost 8. It takes about 4-5 minutes for me to get it to eight and that's with a pump that pulls 20, so I know I have leaks to find. At an idle, I think my manifold vacuum bounces in the 6-8 range, but it's been a long time since I took a reading there. My questions are:

How do you build pan vacuum with low manifold vacuum? Do you hold the R's at 3 for a while as often as possible before the run?

Will a variance in pan vacuum make a difference in ET? I run brackets/index races so I need consistency, but I don't want to add a pump.

If these questions have secretive answers, I completely understand.