I thought TPink involved sebecate, which was the special ingredient that makes it different from other non-2EHA OATs.Toyota pink is actually a phosphate enhanced hybrid oat coolant.
In any case, I'd drain the system, break coolant hoses where I can, and use compressed air to remove as much mystery coolant as I could. Optionally, I'd do a flush cycle with water and prestone citric acid solution. I'd refill with Toyota pink or Peak Final Charge Pro...my new favorite long life OAT (which happens to be phosphated and available just about everywhere as concentrate or 50/50.)
The problem with Toyota Pink is it's really only available as 50/50 mix. So if you water flush the system, and you can't get all the water out, you'll always be below 50/50 mix...which may not be a big deal...but maintenance drain and fills will get you back towards that goal over time. I'm a big fan of water flushes, but when going back with 50/50 you are guessing and don't have much recourse if you test the system with your $4 hygrometer and don't like where you ended up.
I know the drain petcock on the rear cylinder bank of our 2GR-FE got nearly all of the coolant out of the block, after draining from the radiator.