1994 Mazda MX 5 Miata Spec Series | Forza Motorsport 

The tune is in the description. However, if you want to use someone else's tune, you can find it in the 'find tune' menu, and it should be available there. Don't forget to check the series' PI requirements, or if the series you're joining is a spec series, you'll need to find a tune with the same PI. Look for tunes labeled 'spec tune' or something similar that compatible for the spec series.

@@ReynDriving It always say the file with the combination of parts is locked, and i must remove, do I have to have a level on these cars?

Just cancel it, don't remove. It's because you can't modify their tune, but you can use them.

@@ReynDriving I will try it. Thanks :)