miss firing on two cylinders
Might be time to take it to a professional. If it's not the coil, then trying too many other things may do more harm than good.
Make sure your plug wires aren't crossed or touching on those cyliders. Ford had problems with misfire especially on 7-8 if they touched.
do a compresion test!!!!
try replacing the plugs and wires
Looking for a Used Mustang in your area?
CarGurus has 45,735 nationwide Mustang listings starting at $1,999.
Search Ford Mustang Questions
Ford Mustang Experts
Related Models For Sale
Used Cars For Sale