I have GDI V6 3500 Petrol. The mileage on engine is 140K. Last time I went for tuning, the plugs were found black, silencer is also full of carbon. Smoke smells really bad. I want to change the plugs and plan to get clean the throttle body so to get rid of problem. The original plugs are NGK BKR-5ETUA with three tips on the top. Could find these plugs in Lahore at montgomery road and checked the Karachi market as well. Kindly help and guide.