Paul, you have no idea what you're talking about when it comes to sludge issues on those engines.
I'm not going back into this issue again as it has been proven more times than you can imagine, but it is a fact that the oil in 96/97 had a major change in formulation from the SH to the SJ and that there isn't a pcv valve anywhere that will shear oil down from a 30wt to a 20wt viscosity inside of 3500-4,000 miles(proven by oil analysis), And no pcv valve will cause a brand new engine to sludge up in 12k miles to the point of locking up. Thier engine design was fine until they implemented extended drains with the use of sj oils. On top of that, they did not enlarge any oil channels. FYI they did replace the oil sump pickup screen with a bigger one only when an overhaul was done as part of their resolve to sludging. They still us the exact same part number for the pcv and no other TD's are out to eliminate this problem with exception of reducing oil drain intervals.
There was a lot of speculation about the pcv valve, just as you are passing it around, but truth is, anyone running 3k drains, had no problem with sludge whatso ever. I believe it was around the same time, 96-97 when toyota started to recommend extended oil drains to 5-7500k.
So in a nutshell, it is/was a combination of all of the above that caused this but pcv was not one of them.
I wish too that you'd qualify your expertise as TheMechanic asked earlier.Seems you have a lot of answers but a lot of unfactual information to back up your statements.
BTW, Some have seen this in person on this board and not that it means anything, but Coporate Toyota in Torance Ca, called me personally, and sent me a real nice mens seiko braclet watch with team toyota on it with a letter of appreciation with the help on the sludge issue because I along with the local ase master mech's did research with analysis and such to make some determinations as to the cause. What most were doing, like yourself, was speculating because a lot are just mechanics with very limited knowledge on oil, the oil's history with the api cert changes and the basic chemisty changes used in oil and how it is affected by mechanical conditions.