engine got pulled and torn down. cylinder #4 that had bad compression and 50% on a leak-down test had a cracked piston. lucky for me it didn't break off completely. all you had to do was scratch at the crack just a bit and then a piece just chipped off. (pics of it posted)
I'm going a different route with the pistons. the bottom end from the B6 miata is supposedly the same as the ZM protege but for some reason two different ZM people had to skim 1mm off their miata pistons to fit the ZM. human error? some variable between the two motors? don't know don't care. no need to risk losing warranties (parts and labor) and alter the pistons.