In the '96 - '97 timeframe, TFS took the TW heads off the market to look into - resolve accelerated valve guide wear problems being experienced by end users.
I got one of the first sets of redesigned TW heads. So far, 12,000 miles, and no noted problems.
For insurance, when I had the pistons flycut, I had them cut for TW heads, and standard valve location heads (Ede, AR, WP, etc.) just in case I had to change.
TFS does require roller rocker arms to use this setup. I used CompCams ProMagnum steel roller rocker arms. Some Mickey Mouse was needed adjusting the pushrod guide plates so the rocker arm roller tip was centered on the valve stem.
Still not sure I agree with using neoprene rubber valve guide seals rather than teflon, or teflon insert seals to control
oil consumption down the valve guides, but time will tell.