This a 4-2-1 header for the NA 1.8L Miata. I installed it on my DP car, but never even started the engine before going in a different direction ($tahl). Warning: the damn thing won't fit without loosening the driver side motor mount and lifting the engine a little-a well known feature of OBX design. $100 OBO.
ps: Had the same installation problem with the Stahl header which cost 6X!
