I have been getting codes coming up Po300, 301 and 302. I changed the plugs, and found out they were detonating. Along with those codes, I have been getting PO 443, Evap purge solenoid Circuit. Although I was told in some cases it is the coil rail, we did a resistance check, and it checked ok. Replaced the plugs, re-installed the coil rail. Have not had the engine misfire codes come back, but the Po443 did. Any ideas on how to attack this???