gp1200x

Does anyone know if the RX timing belt or idlers make noise or vibrations when excessive slack starts to become an issue? I see references to the SC300 with this symptom however I do not know what engine is used in that vehicle. My 99 has 86K miles and I know I am hearing noises and vibrations between 1800 and 2400 and I am wondering if it is the water pump or idler compensating for belt slop. I don't think it is the A/C, PS or alternator but I will remove belts when I get time to be sure. That only leaves the water pump, timing belt or camshafts (or worse yet....mechanical failure). It revs up to 6K and a I notice no other noises or vibs outside of this small rpm range. I'm still waiting for the manuals before I start my teardown. I only want to do this once and do it right the first time. I plan on replacing the water pump, timing belt and idlers while I have it open. Any other recommended parts to change while I am in there?