I have the Trapp slip-ons. I don't yet have the K&N filter. When the OEM filter gets full of GA pollen, I'll probably go with a K&N. I will probably pass on the T-Boost...
I run 6 disks plus the open end caps. I have no problems with backfiring or any other indication of leanness. I haven't really noticed any performance gain from them either. Sure sounds faster tho... :rocket bike: