[ALF]

Hi Paul
I cannot reply on your original question about the mixture screw.

But as you mentioned that it worked perfect before you removed the distributor, to fix an intake leak, I would search on this side again.
It worked before!

Did you replace any gasket or could there be some small dirt in between?
If I would be you I would try to go back with the settings on prior the intake work and check the work you did.
Not saying that you did something wrong.