The SP8 is 100 percent Ion underneath all the plastic. Ion O-ring kits will work. Also, I highly suggest switching to using a regulator and HPA if you can. The regulator threads are industry standard, to pretty much any reg will screw into it and work without issue.
As it sits now, there is no way to adjust the input pressure, or FPS, on the gun. The regulator that came with it on the factory was how the input, and therefore the FPS, was adjusted.