If you are desperate for speed and are wondering if any of your greys have a hidden speed secondary, then you may as well bump it all the way up to 12. The first 12 levels of a 5* cost about 120k, while the last 3 cost 360k. But the most speed you will get out of it is +5 if it is grey to start with.
If you have a green L1 mod with a speed secondary showing, you are guaranteed to get a speed boost to finish somewhere around 6-10. Level up to 3 to see the final speed.
If you have a blue L1 mod with a speed secondary showing, you might get a speed boost or even two. Level up to 6 to see the final speed.
For a purple L1 mod with speed, level up to 9 to see the final speed.
For a gold L1, level up to 12.
