Mystery Noise Challenge!

Ok, here's the deal. I have an 08 Tacoma TRD Sport. Specs: 6" lift, 4:88 gears, 6 speed manual. I keep hearing this noise that is more prevalent at high speed (5th & 6th gear). It can be heard in lower gears but definitely not as loud. It happens as I'm lifting off the throttle and sounds like a chatter, kinda higher pitch. Does it for a sec and once the load is off it goes away. I also get a noise in the same situation in 4wd but it sounds more like a growling (gear) noise. I recently had a new clutch and throw out bearing installed. No help. When I had that done the transfer case and rear differential were taken apart and inspected. Nothing found. I also recently replaced the carrier bearing. Any help would be greatly appreciated. Its driving me crazy!