Mine is the 'Slip on ' System and the people I spoke with at Projex seemed very professional and on the case, whereas others seemed a bit vague.
I don't normally like aftermarket modifications, but I am aware of the quality of Akrapovic's products and their working relationship with leading manufacturers, inc Renaultsport.
Mine will be a subtle enhancement - saving some weight, crisper exhaust note, touch more power and torque. I probably won't fit the Akrapovic tail pipes, to keep it low key.