What do you guys think?

[RipMr2]

Need some opinions on what this noise could be.

1990 Nissan 300zx TT with a 96 TT motor. Previous owner did swap.

Owned the car for a little over two years with no major problems. I do take it to the drag strip two to three times a year.

[youtube]http://www.youtube.com/watch?v=UIhWTAIfFPg[/youtube]

Quick story on how this noise came about. Last November, I was getting ready to put the car away for the winter and did an oil change. I drove the car once that day and had no issues. I filled it with Royal Purple 5w30 oil with the filter full of oil and the dip stick read full. Started the car and listened like I normally do and heard no issues on start up. No lifter noise. Nothing. Never revved it up and walked away for about five minutes to let it warm up. Came back and was going to drive it around the neighborhood to make sure everything was good. Revved it up to 3k and sounded great. Put it in reverse and started hearing this noise. Awesome. I did not drive it and put it back in the garage and made this video. I'm not sure if I accidentally starved the top end of my motor of oil or what. My oil pressure sending unit wasn't quite accurate all of the time. Sometimes it would work and sometimes not. There was a dent in the oil pan around the drain plug but haven't had any issues or noise because of it. I honestly don't know for sure what's going on. It does this when it is warmed up and not cold. Just need some extra opinions on this. I never pulled any coils, checked timing or compression like I should have before I pulled the motor. A couple others looked at it as well and they also said bearings like I thought but it isn't. I just assumed it was and now I'm here.

Things I've already done:

Checked bearings and clearances. All meet specifications. Bearings are not cracked or in pieces.
Checked crank. Zero scratches or marks on the crank. Looks great.
Swapped all lifters. One lifter that seemed stuck was in the general area that the noise was coming from (passenger side valve cover area). But I'm not sure if it is lifter noise.
Changed the oil pump, oil pan, pickup tube and oil sender unit.
Changed timing belt to a Gates High Performance Belt.
Checked the flex plate and no cracks or obvious issues.
I feel like I'm missing some other important things but I've done a lot.

Things I haven't done:

Never pulled the heads. Never did check wrist pins. You think it could be a wrist pin finally giving out after revving it up to 3k?
Did not check compression or pull any coils to pin point noise (I used a stethoscope).
Did not change oil once more before pulling motor. I really hope this would have not fixed this problem lol..
I think that's it.

Now I haven't even got the motor back in the car yet. I've painted the bay and doing all of the misc stuff at the moment. The motor is back together except the oil pan just in case I do extra work to it. So I'm not even sure if I've somehow fixed the problem but I believe I haven't yet since I haven't seen anything wrong yet.

Thanks guys.

Mods at the time:
K&N Intake
Full 2.5" exhaust
SpecialtyZ ecu chip
740cc Nismo injectors
Unorthodox crank pulley
Hard pipes
GReddy boost controller with two settings: 12psi and 14.5psi
HKS Turbo Timer
Some other misc Z1 hoses here and there.