The top pic has very transparent bursts going on, but you can't see the core of the flame - that's hidden within the exhausts and they are much shorther because of that. Your flames are long enough to have a core.You might want to add point lights in the exhaust (or a luminous material).
If you do see something that looks gray (tried to look for it, but didnt find anything), then it's most likely because the pic comes from a video and there is some sort of frame blending going on or the sensor being bad.
I know it hase notting to do with LFS.
but i like it a lot and want it to show to you
what i have change on the car.
Letters and logo removed
roof spoiler kaminari
Side skirts: Veil Side
trunk spoiler: Do Luck
rear spoiler: Do Luck
Brake light: Smoky
Exhaust: I thought Irmscher