MY 1986 GT V8 MUSTANG RUN SLOW AFTER IT WARMS UP WHAT IS WRONG?

Hello LDOGG-- It's always tough getting beaten by your own brother. At least that's what my brother tells me. Seriously, your problem has several possible causes. Check the easiest possibilities first, like a dirty air filter or fuel filter. More difficult problems could be with the fuel pump, the throttle position sensor or the mass airflow sensor. It sounds like you need a professional mechanic to get you the answer. A good one should be able to help you very quickly. Good luck from Bovan.