its supposed to give a better mix of fuel and air before ignition. i spent the extra and went the nismo route as its a direct drop in and plugs into the factory loom.
factory clutch switch with a 12v feed into it and then into a DI input on the ecu. don't remember which way it works clutch in for 12v or 0v but that's all changeable in the ecu
the RIPS gear does use stock parts. however, they do not just take a stock block and slap a head on it, there is lots of prep to the bottom end to get it to do what they want.
If you have a spare DI that should fix your issue with dropping boost on shifts, mine holds full boost through shifts with it on. If you are referring to the plug on the switch for the clutch i just cut the wires and soldered new ones to the ecu.
changed the fluid over shortly after i got the thing and that brought 4th back to life for a while but its getting a bit notchy again. 5th didn't change at all with the new fluid.
You don't HAVE to change it, its just by the time you add in the Z32 or Q45 AFM/s and a boost controller you're at the price of another ecu with far more features.