Strange Noise

[greenhouse]

Any Ideas as to why my car is making the following noise: When revving and lifting off when reversing down alley where i live i get the usual dumping sound but also getting a bit of a pop / bang sometimes very loud it sound sort of like a gun shot? It doesnt happen all the time and i think mainly when the car is hot! I have fitted a Supersprint back box (not even cat back) to the car a few hundred miles ago but it has only recently started doing this at first i thought it sounds good but worried now something may be wrong? Anyideas as to why it makes this noise?

Thanks

 

[Dan Cupra R]

Its the unburnt fuel going through the exhaust thats making the popping noise. Its nothing to worry about, I get it all the time when my exhaust is hot and I let off the throttle.

Its nothing more than unburnt fuel my friend

 

[greenhouse]

See thats what i would have thought at first but it can be loud sometimes! When i spoke to a mate who is a mechanic he started talking about maybe Cambelt might be causing it and when i tried to show him noise it wasnt doing it maybe because it was cold! But he listenend to engine bay and said it sounds like it was running well so he then said prob not cambelt! Hopefully just unburnt fuel but like i say bangs/pops can be loud!

 

[Steve GTI]

Mine used to do that! And it was a std exhaust!