I don't know if it can be. It's most likely the exhaust heat effect, I think there was a bug where you see that, are you on the latest build?
Is a weel know bug by devs,same bug affected the screens on track too,i hope they fix this one too soon.
I have this same bug behind F4 Tatuus, Post process ultra. I think it's a bug related to heat haze effect. Recorded at Nogaro (Pixsim track).