Heres my opinion on all this, the reason there are so many posts on seafoam and cleaning the TBI and IAC is because it is one of the few genuine problem issues with our Camrys. Toyota designed the engines so the PCV gases (sorry for all the acronyms oy) go straight into the plenum. And after many miles there is buildup but usually does not do much harm for a long time. Modern engines run hot enough to burn away the effects from any problem areas including piston tops and valves, with one exception, yep the throttle body butterfly and Idle Air Control valve.
There are several easy solutions and none take much work or have to be done very often.
1. Per other peoples posts - you can simply cut the hose between the PCV valve and plenum, and install a clear universal fuel filter which cost about $3.00 plus a couple hoses clamps. (Ifyour engine idle funny after this maybe you pointed the filter arrow the wrong way, lol, gozinta engine.) And this will catch most of it.
2. If you remove the plenum for other maintenance, such as cylinder head or manifold work etc., then and only then soak it but good the inside with seafoam or carb cleaner and roto rooter it with paper towels, gun patches, what have you. Just get it as clean as you can and then forget it. Personally i wouldnt remove the plenum just for this cleaning, i dont believe its necessary.
3. Clean the TBI butterfly and IAC. (Dirty IAC shown in image above)
(If you use the fuel filter trick, the need for this ought to be minimal.) But after about 40 or 50k it will probably need it - and your idle might one day start to get rough and you will wonder why, and so you might wind up spending $$$ to find out when the only problem could be, dirty TBI/IAC. And the mechanics you take it to will no doubt, be very glad to take your money to fix it, when meanwhile, maybe all you needed was a $5 can of intake cleaner and a screwdriver to remove the big hose clamp off air filter tube and clean this thing.