Due to air leaking, is how long in time/miles it was as the leak would cause real lean AFR and cause PCM to command far more fuel injector flow which would cause more carbon buildup, and you should use a decarb product in oil and gas to help clean out and check spark plugs for carbon buildup, this also would help clean the fuel injector nozzles from carbon
Also with that PCV connector not correct would cause PCV system not venting oil fumes correctly