amount. Also do a vacuum test with the engine warmed up and running. At idle should read a very steady 19"Hg and at 2000 rpm a very steady 20.5"Hg (these are my 92 NA readings, same since 1992 and now at 73K miles). Vibrating needle indicates a problem the larger the vibe the worse the problem. Research a repair manual or the instructions for the vacuum gage for needle interpertations.