exhaust knocking

[scoota80]

well ive eventually got my cat back on for m.o.t time this week, but now under hard acceleration i get a knocking noise, sounds like the exhaust is knocking against something, i never had this problem when i had the decat fitted, any ideas?

 

[JoedotwasT5phy]

Heat shield possibly - easily knocked off/loose. Checked the clamps?