There are NO power gains to be had with any aftermarket CBE on an MS3 with the stock turbo. NONE.
The stock CBE flows better than the max exhaust flow rate of the turbo on the '07-'09 models and this is likely true for the '10. Mazda got the CBE right.
The exhaust restrictions are bad, but they are all ahead of the CBE. To make power on the exhaust side you have to remove the horrible sharp right angle shape of the stock downpipe and the two low flow cats.
That means an aftermarket dp and rp, catted or catless. You will get a serious power gain that way.
CBE upgrade only changes sound on this car unless you have mods pushing you beyond 300 whp or about 340 crank hp. That requires a bigger turbo and custom ecu tune.
BTW: Your first mod should be on the intake side, not exhaust. The stock airbox is extremely restrictive. Any good aftermarket intake will gain you almost 20 horsepower. You need to create more airflow into the engine before any exhaust mods would be worthwhile for power gains, anyway.