Whirring engine sound

So, about 2 weeks ago I noticed an odd sound coming from my engine. I have had this car since July and its never made this sound before. (First off its a 2000 Accord EX V6 Coupe) My car is complelty stock and it started making a whirring sound that occurs when I accelerate...I mainly hear it at low RPM's but it continues through the high end too. I have also noticed a slight lag in my 0-60's and such, yeah...I punch it a lot. So, I took it into MINEKE and they have a history with our 98 corolla so they took me in and had 2 guys under the hood, they found nothing at all....they checked everywhere one guy even got out a stehescope looking tool, and said he heard nothing wrong and my car is in top shape....am I just being over protective or is there something wrong the mechanics are missing?

Noises like that I always take the serp belt(s) off and run it briefly and see if the sound is still there. If it's accessory belt driven noise, you'll know because it will be gone. If it's not, it'll be easier to hear and isolate without the noise of all the belt driven items...

Pay close attention to the timing cover area, fluttering timing belts and bad tensioners can produce that type of sounds...