Hi. I got the MSD 8477 distributor and got a few problems with it. It's installed with the light blue springs & blue bushing. The idle advance is 10°, getting to 31° max at 3000 RPM. When I tried to check the advance in 4000 RPM it showed 31°, but when I came back to 3000 RPM it suddenly showed 21° advance. Left the gas pedal and then raised the RPM back to 3000 and it showed me 31° advance. Other problem is when I try to connect it to vacuum source. The car start stalling and jerking wanting to die. The vacuum source is manifold vacuum. Tried to apply vacuum with a manual pump and even the slightest vacuum making it behave like that. With the vacuum pump I got it to advance to 16° and it still behaved like that. When I try to put the distributor itself at 16° advance the engine works normally. After few test I found out the vacuum amount doesn't matter, even the slightest vacuum without any advance still make the engine stall. I'm guessing the it's not the vacuum advance, but the action of applying vacuum making it the distributor acting weird.