YODAONE

2 valves/cylinder generate better lower RPM power than 4 valves/cylinder.

An article by David Vizard presents this infornation in detail;

http://www.motortecmagazine.net/the-future-of-4-valve-engines/

Vizard's article proffers using 4 different valve sizes will improve power across the power curve. (peruse the article)

While undecided whether to employ PolyQuad to my cylinder heads, elected to research availability of off the shelf aftermarket valves and valvetrain components that are not manufactured in China and offer improvements over OEM.

Supertech Performance catalogs 1.5 mm oversize intake and exhaust valves for VVTi and are advertised to fit 1998+ 1UZ-FE, 2UZ-FE and 3UZ-FE.
Engineering drawings of intake and exhaust valves attached as .PDFs below.

Also see:

http://www.supertechperformance.com/

They offer a full complement of valvetrain upgrades: valve springs, retainers, cam followers and valve lash shims.

I especially like the design of their cam followers;

Supertech employs a "pad" beneath the cam follower where the lash shim can nestle. This design is superior to lash shims centered in the valve retainer.

Undeside of 1999 LS400 cam follower pad does not center the lash shims.

***** Tagliavini at Supertech explains; the benefits;

"In Toyotas and other brand of “under the bucket shim”, the shim is retained in a recess made on the spring retainer.
In high performance applications where there could be some valve flotation or the use of a Anti Lag system pushing the exhaust valve open, the valve and cam follower tend to separate leaving the shim behind in the air, from the inertia, and coming off the retainer.
In our system with the shim located in the cam follower, the shim always stays with the cam follower, even if they separate from the valve, and even if the shim is facing down, because there is a tighter fitment that with a drop of oil will never come off unless you use a magnet to remove it."

1990 - 1997 1UZ-FE employed lash shims between the cam and (atop) cam follower, while 1998 1UZ-FE VVTi placed the shims between the valve stems and the cam follwer (beneath)

Toyota's redesign acknowledged that shims atop cam followers were prone to shifting.

However, 1998+ 1UZ-FE, 2UZ-FE and 3UZ-FE also requires removal of camshafts to adjust valve lash.

Am contemplating replacing all 32 valves with Supertechs oversized valves.
Am advised the stock valve seats can be used.

Welcome constructive input or questions.

Thanks.