whats that noise !
 

After hard acceleration when i release the gas pedal to change up sometimes i hear a noise a bit like the dump valve on a turbo,a kinda pressure release noise the car runs fine otherwise any ideas what it might be?

exhaust leak?

Cheers CDiercks the car "burbles" nicely at low revs but is pretty quiet at speed,ive had cars with worn baffles/blown exhaust and they are generally a lot louder all the time the noise im getting is just as i get to red line and release the gas to shift gear.

The only reason I mentioned it is that I just replaced my cat with a premuffler and have the same sound. I forgot to get new gaskets, and installed it with the old worn out gaskets until my new one show up on my doorstep. When the engine is cold, every time I shift I get that exact same sound you describe. Best of luck as I don't know what else it could be.

Cheers will get the exhaust checked out :)