Used EGR block off kit for 1999-2000 Mazda Miata taken off my car as I upgraded my header.  

The block off for the intake manifold side (good for 94-05 1.8L engines, as verified through Racing Beat and Flyin Miata) is hand made out of thin aluminum-- not sure of the thickness but it was leak free.  

The plug for the exhaust manifold side uses an Allen head to tighten and goes into blocking the EGR port.  Again I upgraded to the NB2 header so I had to remove the kit.