We wnat to tile our kitchen, but the floor is uneven (not all the joists were crown up), and has a lot of bounce in it( minimum sized joists were used). What is the best way to beef up the joists? Should I use engineered I-beams or just sister another 2x to the existing joists? what is the best way to lelvel the floor? Should I remove the worst sagging/crowning joists? They are constructed with the joist on top of the main carrying beam, no joist hangers were used.

Strengthening floor joists