The only company that was making under drive pullies was WRP. They no longer make them for the titan because it was causing cracked flywheels. They didnt have them balanced so the vibration would crakc the flywheel. No one has tried since.
Last time I looked, he still advertised it about a year ago. I almost got to meet the fella, as he uses a shop I know, to work on his car. AVOID the WRP Crank Pulley, as it has no harmonic balancer. I still have the Power Steering Pulley mounted, but it was only UD by 1/2% vs 10% advertised, because he used the wrong drawing when he had them made, and never corrected the error. AVOID William Peridgon.