I have american standard trane heating unit . The heat exhanger pipes clogged in front burners . The heat exchanger pipes don't have screen over it but some type clay inserts atached by clip there is 1 for each pipe what is this part never incounterd bfore this unit made1997 it is ycc model outside unit

You have a high efficiency heater. One tube is for intake air, the other for exhaust
Very common to have mud wasps put their tubes in there. Clean out the mud, lightly flush with water and put hardware mesh, 1/8" over the ends.