The RTD thermister EGT used in the EGR system looks very different from the usual high-temp fast-response thermocouples used for performance gauges... Is the entire assembly rated for 1800F or is that what it is capable of reading? From the pictures, the wires coming off the EGR EGT are not shielded from heat, so they don't look like they'll last if mounted on the exhaust manifold...
Also I think the EGT used for the EGR system does not have to be of the fast-response type (which are more expensive), so that's a question mark there... you definitely want a fast-response thermocouple if you are trying to measure cylinder exhaust temps.