I'm trying to find a plug for this hole on my manifold and I can't figure out what thread type it is. Also, does anyone know what thread type the EGR exhaust line is? I think it's the same as this hole. Some metric pipe thread?

The dealership says it's 3/8 NPT but the plugs I bought don't fit.

M14

 

Stick a sparkplug in it lol

Good one, G.      Not only would that work, but would be a great conversation piece.  Make sure it is NGK.

Subaru's new 5-cyl.

+1 on spark plug. You might wanna bust the ceramic in a safe work practice and weld the hole up. Or get another coil and lead

I just left the thermosesnsor in there. You could try to take the thing to Fittings inc. to find a plug to match. They would have something I bet.

It's not m14. I can make something work but I want something that looks clean and proper. This is my 4th weber swap and I don't like jimmy rigging things like I have in the past. Before, I would cut the thermo sensor flush and put it back in and I would also cut the EGR line and fill both of the fittings with high temp silicone and use those as plugs but even though all of those meathods work great I want it to look profesional. I plan on doing many more builds in the future so I am trying to streamline the whole process and work out all of the kinks that people usually just "work around". Once I find permanent solutions to all of these little problems I plan on making a step by step guide. Thanks for the input! 

Try Fittings Inc. They will have it, though you might have to bring your manifold in. They are is the Sodo district in Seattle on 6th ave S.

Mine all have a Hex plug in that hole. 

I've had one car that had a plug and I couldn't get it out. not sure what the difference is and why some cars have a plug and some don't.