I have a carburated '91 305 with an older Holley 4160 600cfm carb. My vacuum is at about 18. It idles in park at around 1500, when I put it in gear, the idle drops to 600, oil pressure drops to about 10 and the temp goes from 180 to 200 pretty fast. How can I get the in drive idle at about 900-1100 without having it at 2000 while in park? I have followed the idle adjustment procedure. Moving the mixture screws to 1 1/2 turns out and then adjusting both sides evenly, then adjusting the idle screw. Any ideas, or anything I am doing wrong? Thanks in advance for any help!!!!!