The curve should be pretty much a straight line with about 15 at idle down to about 0 at full throttle. full vac at idle is a function of one of the vacuum switches on the valve cover ( the lower one I believe) as you come off idle that switch closes and vacuum is controled by the vac control modulator on the back of the Injector pump. it sounds like your vacuum switch is working to give you full vac at idle. your vac. cont. mod. doesn't seem to be working correctly though. The vac. cont. mod. is adjustable if you remove the cap just forward of the lower vac line you can adjust it. only small adjments. you might also consider removing the vac. cont. mod. and taking it apart and cleaning it. having said all this quite alot of the vac. cont. mod.s are just plain bad. it's plastic with a spring in it and it's over 20 years old. there are a few articles available on adjusting the vac. cont. mod. MBZ.org has a good one and steve Brotherton did a really good artivale on adjusting it. do a search on it, there a few threads with links. Good Luck

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Kevin
82 300D