Shaun Van der Linde is a well known tuner in the racing circles and they do magic on most motors. The conversions are normally done in 2 stages and are based on gas flowing the motor and 'chipping the management.
A full conversion would involve gas flowing the heads and intake manifold, cutting or replacing the cams, adding a free flow exhaust system and upgrading the management with a Dastec Unichip or something similar. The chip gives these guys more parameters to play with and the motor can be more finely tuned in specific ranges.
This is one of the more reliable upgrades as these guys are very knowledgeable and you will not be stuck with a motor that can do 1-100 in 0.blob sec but not have power lowdown to climb a sidewalk.
On a 3l they produce about 25 kw additional, not something to sneer at, but the most important point there is no negative side effects.
Enjoy hat baby it is a "Lekker" upgrade