The 1098 is known to be hard to modify to meet Nordic noise regulations, the pipes are too small. My bike came with GPR slip-ons and I ordered DB-killers from S-racing. These GPR original parts seem to do the job well, no noticeable power loss and I have passed numerous noise tests this season. Stand still measurements as well as drive by (95 dB is the limit for Swedish race tracks).
Simple design that enables good flow to keep power levels up. Easy to mount just a clip (In Swedish Segersäkring)