Mazda tuner BBR has developed a range or engine and suspension upgrade packages for the Mazda 3.
The performance packages are available in three tuning stages and address the 2.3 DSI turbo engine which is also found on the Mazda 6.
The entry level BBR Mazda 3 upgrade is priced at 549 GBP and consists of an ECU remap which enables the engine to deliver a ‘dyno proven’ 290 bhp at 5,200 rpm and 300 lb-ft of torque between 2,850 rpm to 5,100 rpm (34 bhp and 50 lb-ft more than the stock model).
In phase two the BBR Mazda 3 receives a custom fuel pump that increases fuel flow without affecting pressure as well as a high flow performance filter that replaces the stock paper airbox.
The car’s restrictive MPS turbo downpipe, the pre-catalyst and the main catalytic converter are also replaced with a BBR3 stainless steel downpipe incorporating a sports catalyst and as a result total output jumps to 300 bhp between 4,300 and 6,200 rpm and 370 lb-ft of torque at 3,800 rpm. 
This phase two power kit is priced at 1,645 GBP and also carries a 395 GBP fitting charge.
For those who consider that 300 bhp are still now enough, the is also a third option : the BBR Mazda 3 Phase Three kit which offers two offers two turbocharger upgrades options in addition for the Phase 2 conversion.  
The first turbocharger is a overhauled unit from BBR featuring a high flow compressor wheel which enables a total output of 350 bhp while the second option is a Garret hybrid GT28 turbo charger that takes performance levels to 350 bhp plus.  
As for the suspension upgrades we mentioned earlier, the BBR Mazda 3 can be fitted with a performance spring set or alternatively a set of adjustable dampers from Koni.

Source: BBR