The first place I would honestly look is the throttle position sensor. It is about the only thing I can think of that would affect both the transmission and the fuel trims. The transmission uses it to determine the map of when to shift and how firmly to shift, then the shifting itself is determined by any one of these components:
- Fluid temperature sensor
- Pulse generator A (PG-A)
- Pulse generator B (PG-B)
- Shift control solenoid valve A (SCSV-A)
- Shift control solenoid valve B (SCSV-B)
- Pressure control solenoid valve (PCSV)
- Damper clutch control solenoid valve (DCCSV)
- Shift stage synchronizer
- Ignition pulse
- Throttle position sensor
- Transaxle range switch
I would also try something else. With the key on, see if that noise is the same while you have the accelerator floored, and then try the same thing with the TPS disconnected. That's not a scientific diagnosis, but if the sound changes or goes away, there's a good bet that its your problem.
Another thing you can do is simply test the TPS. Values should look like this:
Voltage to harness terminal 1 = 4.8-5.2v
test continuity to ground from terminal 2 = less than .5 ohms
Using your code scanner, test TPS voltage output. At idle it should be between 0.1 and 0.875v. At WOT it should be between 4.25 - 4.8v. If your scanner doesn't return voltage values (if it just gives percentages) then you can hook up the test voltage from term3 to ground with the key on, or test ohms between 1 and 3 for smooth operation.
Otherwise its a tough one. Keep us updated.