can this be restored by heat gun or something I heard it was possible? mine is chalky and discolored and I do not want to buy a brand new pair

 

Old/faded/chalky HARD black plastic exterior parts can sometimes be redressed with a heat gun. Difficulty: if you linger too long or use too high of a heat, you will damage the part. SOFT plastics like door seals I think would tend to melt and deform much easier. Check youtube for examples.

 

On all external black plastic, rubber around windows etc., I spray some tire shine foam on a towel and wipe it all over that part to make it shiny black again.