Hey speedwaymaniac
Most B6's (including mine) have a nasty batch of resonant vibration between 4000 and about 5200 rpm. This engine vibration can be causing something else to resonate, usually the fairing, windscreen or gauge connections.
I would also look under the tank for anything rubbing, loose. Check the around the airbox, etc.
If it truly is coming from the engine and has increased in sound/vibration, I would suspect the cam chain. The tensioner should be automatic, but they can get sticky, and/or worn from age. You can sometimes loosten the adjustment locknut and tap the tensioner bolt and area "very gently" with a plastic tipped hammer, or similar, and see if it frees up. You would want to do this while turning the engine over by hand, so as to ensue the drive side of the chain is tight.
Otherwise you are faced with removing the top head case cover (like when you check the valves) and checking the condition of the chain, sprockets and tensioner.
BUT, like I said, because this is such a common rpm for this engine to vibrate, it is likely something else vibrating along with it, and making more noise than usual.