Noise when reversing or high revs

[mattlear23]

Put my cat back on today as my m.o.t is next week. Had a decat fitted before. I noticed when driving back today that there is a thud from underneath the car when in high revs or when I'm reversing.

The decat didnt make any noise like this before so I'm curious if anyone knows what it could be?

The Gearbox has just been replaced so I'm pretty sure its nothing to do with that

 

[Russ_16v]

Id gurss the exhaust is now knocking against the car mate

 

[richd]

could be an engine or gearbox mount

 

[mattlear23]

The exhaust wasnt being held on the centre hanging mount before. But now it is, think it might just be banging? should I take it off the mount?