K03s with saab red injectors, good turbo back exhuast,silicone turbo intake pipe, a good filter with no boost issues and good maf should see 230bhp plus easily.
Then youl need other supporting mods such as forge actuator to hold the boost,
A good intercooler to keep temps low and improve torque(ths frount mount, ebay special etc),
Maybe bigger maf such as VR6 (3inch)
A nice catch can to replace the sh!tty pcv system,
The above should see a nice torque figure and around 240bhp plus on a k03s after a good remap by a good reputable tuner.
K04 is big bucks and look at toby's build thread.