Did you replace the air filter? I would also do the Fuel filter.
i am waiting for the air filter to be shipped to me. ordered a dna air filter. i did a little sea foam as i mentioned. have checked the fuel filter, where is that at on the bike. also, i got to work and heard the noise a bit after i got off the freeway and took off from a light when i got on it a bit. when i pulled up i noticed something odd on my gpr exhaust.
so to explain, i have a gpr slipon, i removed the db killer so all that is in there is the larger diameter pipe, inset in the tip, that inner steel pipe seems to be loose so i think that may be causing the rattling sound a bit. so i put the bd killer back in with the c-clamp that fits in the slot to hold it in place, that will also push in that inner pipe and hold everything in place. we will see if i hear that sound on the ride home. that inner pipe in the muffler vibrating and rattling could have been making that sound but not sure. i will let you know my findings.
unfortunately now is will be quieter but if that was the noise then i just need to figure out how to re-adhere that pipe inside so that it doesnt rattle, or just keep the db killer in. but i love how it sounds without it.
btw, even with the small dose of sea foam i added. it already runs smoother and i seemed to gain a bit more of top end back, cant wait for my new dna filter to get here