your tach is electronic, if I recall correctly.
If you roll forward at 2-5 mph and tap-tap-tap the front brakes, is the noise still there?
If so, look for a loose wiring connector or your steering head bearings.
2 of my TLs suffered from loose headlight brackets, try that too.
My front race rotors were REALLY loud at low speeds, in city traffic. Are yours stock?
Also, check your chain as it is a very tight left side bend on those TL's.