把刑事現場都打掃完畢了再叫人去找罪證？

I can only tell you they have nothing broken. The critical piece of evidence is the codes you got but they have nothing to do with any of the plugs. Spark plugs never talk to ECU, only ignition coils do. So your codes were from the coils not plugs. Plugs live or die ECU doesn't know nor cares, as long as coil ignites ECU is happy.