Aurelius, believe it or not, I'm not running out of money anytime soon.... not that it is important.

When I turn the wheel when the car is stationary, the vibration gets much worse, so I think it definitely could be the power steering pump.

I'm on a first name basis with pretty much every BMW indy in the San Diego area, no one has been able to solve this problem. Just like on this board, this is something that has eluded everyone, forever.

I've noticed that the vibration only occurs when there is a load on the engine at idle, by placing it in drive or reverse with the brake on, and when that happens the rpms drop about 75 from 780 to about 705, and occasionally into the 650-700 area when the AC unit clutch activates, and the vibration gets much worse.

Are the rpms supposed to drop that much when the engine is engaged/loaded by the transmission?

I had a similar issue with mine. I swapped out the motor mounts and that took care of most of it. Then replaced the power steering pump and that pretty much took care of the rest of it. That drop sounds normal. You can adjust the idle speed if you have the correct scan tool. I bumped mine up before I changed the mounts and pump and that helped. It now is set to run where the factory wants it to run.

The RPMs may drop that much (I have a manual so I don't know exactly, but that sounds right) but that may not be causing your vibration. The engine mounts act as a band-pass filter, transmitting vibrations in certain RPMs but not in others. The engine mounts, especially ones that are faulty, worn out, or just cheap, transmit vibrations in the low RPM ranges. The engine is making the same vibrations as any other RPM, but at lower RPMs they are just transmitted to the cabin better.

Power steering pump getting a load (by turning the wheel when stationary) or turning the AC on, or putting it in D or R with your foot on the brake, these things will all lower the RPM.

You said you replaced them already, what brand did you use? Also did you replace the transmission mount? (I think there is only one on top of the trans)

I concur with Fifty150hs, I would double check the engine mounts -- I have had cheap brand RockAuto engine mounts that were bad the moment they came in the mail (for other makes). I would also agree that you could try raising your idle speed to try to alleviate the problem.

The engine mounts were replaced with BMW mounts 30,000 miles ago, and then at 15,000 miles ago, just to make sure it wasn't the mounts. The transmission mount was also changed with OEM with no difference.

This is a major problem with the M54 engine on the E46 forums, and no one has been able to figure it out there either.

I did find a couple places that sell ECUs that have them reprogrammed to raise the rpm to 900, vs 650, and I think I'll try that.

Has anyone ever used a tuned ECU? I searched for ECU in this forum and it said the search term was too short.

https://revmatchmotorsport.com/tunes/p/e46-tune

https://www.redline-motorsport.com/product/ms43-tuning/

My scan tool will allow me to raise the rpm's to 800, I think. I have it a t about 790 now. It helps, but it doesn't go away. It is far more noticeable when idling in gear. Makes me wonder if it might actually be a torque converter issue?

It isn't the torque converter. I replaced the transmission with a rebuilt one, including the TC, and it made no difference.

Any discussion on the E46 forums about changing the harmonic balancer?

No, the mechanic I went to last said that if the harmonic balancer were the problem, then vibrations would get worse at higher rpms.

Not much...I am on the E46 forums and it does not come up often...