Rear end problem help

Bearings don't care if the power is on or off; they will not sound any different under power than coasting.
I have set up hundreds of rears and every time it howled on decel, there was no making it better; the pattern is crossed up, and there is nothing you can do about it.
Furthermore, you can see the pattern is crossed up in the checking grease before you ever send it out.

Having said that,a mild howl on decel, is only annoying. In a hundred thousand miles it might change a little, but it will never blow up. I got a set of 3.55s in my car right now, that have been just noticeably howling on decel, for decades. I traded a nice set of dead-quiet 4.10s for them too.
I hope you have better luck than I did, getting out of the deal.