Toyota - Tacoma - Suspension - Noises :: Clunk Upon Acceleration Occasionally

I have an '04 TRD Doublecab 4x4. I first started hearing a "clunk" upon acceleration, but only occasionally. It started getting worse and would happen pretty much every time I accelerate (although it never got louder, just more frequent). It usually only happens after a full stop (or near stop like in stop an go traffic), and I'd hear it pretty much right when I step on the gas. It seems like it has something to do with the A arms moving forward and back. When you accel, the rear wheels push the vehicle, essentially "sucking" the front wheels back slightly. When in 4wd, the noise is still there. It is quite obvious it's coming from the front right corner. I'm usually pretty handy with a wrench, so I decided to swap the upper A-arm bushings and upper ball joint (ball joint was leaking grease). Noise is still there. I ran out of time/motivation, so I took it to the Toyota dealer.

Here's what they did: -replaced front right coil-over, said it was "loose". That didn't work, so they put the old one back on. -tightened bumper etc..., didn't work. -then they removed the REAR drive-line and put it in 4x4 and drove it around. They say that "fixed" the problem since the noise went away. They were pretty adamant it was the drive line, but I didn't believe them since the noise is OBVIOUSLY coming from the front right. It just seems odd that it'd be the drive line. I took it home and tried what they said, I took the drive line off and drove it around in 4wd. They weren't lying, the noise went away. But since a good friend has an identical truck (but an '03) I switched our drive lines and the noise came back (HA! I was right!!). Driving in "front wheel drive" (no drive line) makes the front wheels "pull" the truck forward, vs in rear wheel drive, the rear wheels "push" the truck, and thus the front wheels will move backward slightly because of wheel/bearing friction.

I think it has something to do with when the front wheel is forced "backwards" but as far as I cal tell, all the suspension components are intact and show no signs of looseness. I can now occasionally hear the noise when under slight accel going over studder bumps like street reflectors or something (but only rarely, it's almost impossible to duplicate that on command. Makes me think a suspension piece is loose (shock/spring or loose bushing), but I NEVER hear the noise under braking, and rarely hear it on those studder bumps (and only for a split second). If it were a loose bushing, wouldn't I hear the clunk under accel AND decel (A arm moving back and forth)??? So I'm basically stumped (so was the dealer!). Ball joints appear fine, wheel bearing has no slop (that I can tell), and it has brand new upper urithane bushings and a new upper ball joint. I KNOW it's not the shock/spring, b/c I even swapped the left/right, and the noise is still there (and didn't move to the other side).