You posted a TECH question in Talk. This limits your chances of getting some really good advice, since most guys aren't looking for Tech stuff in the Talk forum.
There is no idle air bleed screw on a stock 5.0 Mustang. The computer controls the idle speed once the base mechanical idle speed is set. See the "Surging Idle Checklist for help with all your idle/stall problems. Everything you need to find and fix idle problems is in there.
The first two posts contain all the updates to the fixes. At last count there were 24 possible causes and fixes for surging idle/stall problems. I continue to update it as more people post fixes or ask questions.