Should I vacuum out 1970s insulation before blowing in new?

Hello,

I bought a house a couple years ago that was built in 1971. I am hoping to DYI the attic insulation in the spring time while the weather is more mild.

Should I vacuum out this old insulation, it's about 3 inches max in most places, before I add in new or should I just leave it and blow in overtop of it?

TIA