99 f 250 trouble codes and EGR help

Hello All I need help on where to start, I am doing this work for a neighbor that is down on their luck and broke so I am fixing and buying the parts and don't need to chase the wrong problems. Truck is hard to start and not running the best. I put a trouble code reader on it and got 0308 and a 0401 but the code reader book is universal and I need to double check with someone with a service manual just to be correct. my book says 0308 Cylinder 8 misfire detected and 0401 exhaust gas recirculation flow insufficient detected. plugs have been changed and all injectors too. So I thought besides the EGR vaulve changing plug wires they said truck has no plug wires, I laughed and said then it's diesel right. No it's gas she replied. I cut up with that for a day until I asked someone else wanna hear a good one, needless to say I feel stupid now. Please let me know about EGR valve if codes are correct and is there other part to change with EGR valve? Would a bad coil pack cause this? I guess that is what replaced the plug wires. Thank You for your time!
Eric

Most likely the P0401 is the DPFE sensor that tells PCM if the EGR is oopen or not. They are really bad about failing. As for the P0308, look at the coil boot really close for cracking or carbon tracking.

Ok I will thank you for help would you also change the EGR with what you said to do?

Not necessarily change it, but remove it and clean the carbon out of it and the passages going to it.