Apart from the noise (which I don't want) would there be any performance improvement in replacing the standard dump valve with an aftermarket one?

 

If you dont like the noise, myself included! Get an aftermarket re-sirc valve, no noise and is better than standard jobbie.
The standard ones have weaker springs and can somtimes loose you boost pressure, or something like that.
Forge ones are good.

 

Thanks for the response.
One of the reasons I asked is because I get a lot of hesitation/uneven pulling at small throttle openings around 2500 - 3500 rpm, such as when trickling through traffic. I wondered if this was caused by the dump valve because manifold pressure will be quite high.