EGT Got cold
I went flying did a good climb out , leveled off and set throttle for economy cruise @ 5200 rpm 8 minutes later the engine got rough, lowered RPM and roughness went away. less than a minute later it got rough again , lowered Rpm now to 4600. I noticed the #3 EGT became 330 degrees colder.
what should I look for. when the engine cools down.