I had a 5/16" vaccum hose on a 1/4" barb, it took a year to find that vaccum leak. Ford mechanic use a break out box to test each component when the code reader does not identify the problem. They measure the volt or resistance (value) of each item. I had a after market mass air meter that checked good with the code reader and the break out box, but when my mechanic talked me into replacing it my problem when away. Two books that I use are
"How To Tune and Modify Ford Fuel Injection" Ben Watson ISBN-13 978-0-7603-0503
" Mustang 5.0 Technical Reference & Performance Handbook"
Al Kirschenbaum ISBN-0-8376-0210-6 Ford Racing Part No. M-1832-Z4
You may find them on Ebay or at Barns & Noble
Don't give up. Once you get it run right, horsepower and gas mileage are your friend!
Dwight