Slant 6 dies.

My slanty started dieing at stop lights or down shifting and then slowing for a stop. I idled it up this helped some. But then when I bolt the air cleaner down it runs rough and dies. Take the air cleaner off and it runs good. So I am thinking I need to adjust the air mixture screw? Should I screw it all the way in and then back it out three 1/4 turns and go from there? I haven't touched a slanty carb in 25 years...lol
Try cleaning the air filter element or replacing it.