How do you adjust the A/F mixture on a 93 5.0

The adjustable FPR will help set the fuel mixture at WOT (Wide Open Throttle). The computer takes care of it at all other times. You can get a custom chip burned to change the Air/Fuel ratio for all the activites of the engine, from idle to cruse to WOT.

Why do you want to change the stock air/fuel mixture?