05 PreRunner steering wheel/column -crackling/scratching/sizzling sound at high RPM

Good day all,

I am trying to diagnose a strange noise in my '05 PreRunner (standard cab, 2.7L, MT, 53K miles, stock except for tires, original owner), and my abilities have reached their limit. I've also searched through several forums, including this one, to no avail.

If anyone has encountered this before and has a solution (or at least a cause), or if anyone can offer any thoughts on probable causes and how to check them, I would be most appreciative.

Symptoms & characteristics:

• The noise is a faint-but-audible scratching, crackling or sizzling sound originating from within the cab. It's difficult enough to hear over the engine and transmission noise that I'm not sure if its electrical or not, but it sounds like it may be.
• Sitting the driver's position, it's coming from in front of and below my ears, somewhere around or behind the steering wheel.
• If the engine is cold, the sound tends to be quieter and happens between about 3200-4500 PRM. If the engine is hot, the sound is louder and occurs between about 3500-5000 RPM. Intermittently, the sound will occur all the way to redline in both cases, but I am unable to reliably reproduce this.
• The noise occurs in all gears and neutral, in all driving conditions; steering, braking, accelerating and clutch position make no difference.
• The noise began immediately after I had the vehicle into the dealership for warranty recall service where they replaced the spiral cable and did an oil change.
• There were no other configuration changes or parts replacements within six months of the issue beginning. Subsequent oil/fluid changes, tire rotation, alignment and brake service have yielded no change in the noise.

Because of the spiral cable and the nature of the noise, I suspect something electrical, but since my knowledge of electrical systems is limited to coils, plugs, fuses and bulbs, I'm wary of diving into the wiring blind, particularly since the spiral cable assembly is apparently tricky to work with.

I'm not sure if my phone's mic can pick up the sound, but if it can I'll try to have video in the morning.

Thank you all for your time.