1999 F 250 Misfire HELP!!!!!
 

I have recently bought a 1999 F 250 with a 5.4 and am having trouble with a misfire issue. I have passed emissions with no problems and have no current check engine light on. I ran the stored codes and found cylinder number five and six in the memory showing a misfire. After checking the plugs and boots I found the plugs in good shape and boots falling apart. I replaced the boots and had no results. All eight of the coil packs have been replace by the previous owner. What do I check now?????

A code P0305/P0306 may mean that one or more of the following has happened:

Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Poor compression
Defective computer

What brand coilpack is it?