Cavalier, Calibra, Vectra, Signum, Sintra & Insign
Thanks for reading, here's the sequence of events.
June 2015 : Flexipipe blew through. Replaced, solved.
Knocking started as GM part had straight mounts, but the original had curved mounts.
Assumed centre silencer hitting underside of car.
May 2016 : Rattle has annoyed me, go to kwikfit to get...