Happy to report that after downloading PiTool 259, was given option to update to FW 264 which enabled the 110Hz option PiTool. I enabled the option, HMD rebooted and worked perfectly. SteamVR recognized the 110Hz and tested the new refresh rate in iRacing. Without changing any of my graphic settings (which are high), game ran smoothly with almost no glitches- only graphical glitch was the edge of the tire in the Skippy was flickering- probably something I can fix by tweaking the iRacing settings. Overall the driving experience in iRacing does seem enhanced- feels smoother than at 90Hz as expected.
Nice job with the FW and PiTool update.