I know these are cheap to replace but if you are like me every dollar saved is a dollar you can spend somewhere else.
I had one side that was very warped blocking about 25% airflow over the radiator not to mention looked bad.
1) Make sure your wife is not home (she may not like this)
2)Preheat your oven to 350.
3) Use something on the metal to insulate the grate against the plastic.
4) Insert the guard for 3-5 min
5) USING GLOVES, remove the guard from the oven focus on one spot at a time and hand mold the guard back into the proper shape.
You may need to do it more than once to get it perfect or get all the different issues fixed
Viola! Back in shape!