Your looking at the wrong end
If you want it to growl , get rid of the pre cats and restriction
Even with the rest of the exhaust standard , the car sounds a humdred times better
I don't have one but from what I have heard they do sound quite muted from standard. Most people seem to fit a Miltek to solve that problem
I have driven many R32s and they probably have one of the most tuneful exhaust notes for a standard car IMO - absolutely hairaising
cost is it can be done by yourself if your handy with the tools
a garage would charge a few hours labour to remove the pre cats from the manifolds
to remove the pre cats all you need is a drill and a nice long extension bar
the only thing which will require doing is the lines of code on the ecu need altering or the engine check light will come on
once done it cannot be put back to standard unless you bought new pre cats , but honestly once its done you never ever would want to go back to standard