This is the only one with the issues for me, I really wish there was a way to fix it since I really like it. I've used mods like this one which replaces all vehicles as well (, the links are down now I believe, but I have tried all of those and while I liked them I got a little bit bored after a while, and the handling was pretty much 'meh' at times).
It's probably because this car pack replaces almost all of the vehicles in the game, most other car packs don't even compare. I don't understand why it is with only this car pack that is happens. This is on an i7 4ghz, 1.25gb Vram(GTX 570), 6gb regular ram and an SSD. Every time I try this mod I get issues with texture pop ins, even without any graphical mods.