How to tell if you have the revised liners

[Porkgrisle]

Is there an easy way to tell if you have the revised liners or not? Are the rears really needed and what to they add?

[Porkgrisle]

Dug around and found it, there is a definite cutout above and below the molded indent in the louvered section. Mine were flat so just ordered some from ECS.
51-71-8-051-591
51-71-8-051-592