Why is there oil stain at the joint between Sega's throttle and air filter?

Dear friend, according to what you said, this is normal. Because this pipe is connected to an exhaust gas recovery pipe! The exhaust gas recovery pipe leads to the engine! Besides, your air filter is too dirty. So it is normal to have sludge. It is recommended that you blow the air filter element with high-pressure air several times. This is generally not the case. I hope my answer can help you. Please feel free to contact me if you have any questions. BBA Mercedes-Benz BMW Audi car wishes you a happy life! Happy family! The financial resources are rolling!