Here is my one experience in this area. Oil returns were plugged in a Cavalier. Dad filled the sucker up, to the top, with kerosene. He let it soak for a couple of days then drained it all out. He filled it back up with half oil half kerosene and ran it about ten minutes at idle. Looked like a locomotive started up in the garage. He drained this and did a oil/filter change. It started out ok then lost oil pressure. Eventually found that the pickup screen was plugged with the remaining gunk. while pan was off he cleaned remaining stuff outta the pan and removed valve covers and cleaned in there too.
His only comment was that he shoulda soaked it again in the kerosene cause he figgured it was a clogged pickup. But being as it was about 40 yrs since he had last "flushed" a motor he was a bit scared the new ones wouldn't tolerate the treatment.
So if you have a bunch of sludge maybe it would be best to go at it slowly with several light treatments rather than one megga dose, trying to be done with it all at once. If something breaks loose and clogs a rod journal for example you are in for a expensive rebuild. If you have an oil pressure guage watch it and you may be able to tell when the filter plugs then change that rascal out, and drop oil. repeat the process till you get things cleaned up.
If after an oil change the oil blackens up really fast the detergents are still removing build up. Toyota has had some major recalls lately dealing with this maybe a Toyota mechanic will step in with a good answer for you.
