I'll add an experience that might be the same as James is trying to point out:
I created an account 21/06/2018 and I decided to not update my Design facility, having it lvl 2 all the time.
When my manager level increased to 15 I was racing at Elite with tons of extra car parts, but I couldn't get enough Design Points to make a competitive car.
So, you can stock a lot of car parts when you don't upgrade your Design facility, but you'll rely on research to develop your car. In the other hand, if you don't upgrade your Manufacturing facility, you won't have enough parts to fix your car.
I created an account 21/06/2018 and I decided to not update my Design facility, having it lvl 2 all the time.
When my manager level increased to 15 I was racing at Elite with tons of extra car parts, but I couldn't get enough Design Points to make a competitive car.
So, you can stock a lot of car parts when you don't upgrade your Design facility, but you'll rely on research to develop your car. In the other hand, if you don't upgrade your Manufacturing facility, you won't have enough parts to fix your car.
Thanks for the information:)
