We have brand new TiAL wastegates and they are awesome, you can order one here: http://www.id-workz.co.uk/index.php?main_page=product_info&cPath=696_1097&products_id=2018
Agreed, the Civic rads are good and a worthy investment. It makes life so much easier when working in the engine bay. We have them available brand new.
Welcome along. It definitely sounds like the map sensor from the description, and yes that is a one way valve on the pipe. We may have a spare map sensor here, I'll check and let you know.