Questions on pistons and cams...
 

does anyone know the difference between the Mazdaspeed High Compression pistons and the stock FS-ZE engine pistons? why are the FS-ZE ones priced more?

second question, will the intake and exhaust cams drop right into an MP3 w/o modification? will it trigger a check engine light (since most sites state not smog legal)?

any help is greatly appreciated.

This was answered in several places already.

Stock FS-ZE are 10.5, Mazdaspeeds are 10.7.
No, using both cams will not trigger a CEL. Expect about 7-9 HP on an MP3 with both.