No issues with the frame rate here (GeForce GTX 1070). Even with my older 970 particle streams were never an issue. You could try reducing the source rate (this is the rate at which the particles are created). As for the exhaust, I just thought it looked better without that old thing.
Not everyone has your GPUs. :dry: :compbash:
I'll play with particle streams when I finish the runway files. So are the exhaust textures to go for good? It is kinda drastic IMO, so it should be thought thru.