I've got a fuel pressure gauge that mounts on the schraeder valve on my TPI fuel rails. I need to remove the pin in the valve, then screw on the gauge fitting.

Do I just screw it on? Do I need any type of sealant? Teflon tape? There's a good bit of heat and fuel nearby, figure this had better be done right!

 

I just went out & took a picture of what I did, even though my setup is a little different than what you're describing.

In my case, I removed the entire fitting from the fuel rail & took it in to a local speed shop, who pulled the correct adapter from a shelf that allowed me to attach a short braided line, which allowed me to mount my fuel-pressure gauge on the fenderwell. (No, I don't have the part number, wish I did...)

The valve inside can be removed with your garden-variety valvestem-removal tool, available at any bicycle shop, tire store, etc.

No sealant or Teflon tape was necessary.

Hope this helps!

 

Just screw it on after you remove the valve inside it. NO SEALANT required.