I have sd headers and for whatever reason the o2 snsr is off to the right hitting the firewall causing mad vibration. so i just took a block of wood and a hammer dented the firewall in so the 02 snsr doesnt touch. once in a while ill get vibration but i assume its from everything moving the exhaust slightly that the o2 sns hits the wall once in a while. The vibration is DEFINITLY the o2 snsr hitting the firewall though not an engine mount.