I need help with a BRZ

My friend has a tune on a brz that’s good for drifting (in my opinion) and I noticed that when I’m just driving around I can max out sixth gear and I feel that there could be a seventh gear. Can someone please help me out with telling my friend how to add a seventh gear if it’s possible? The only reason I believe you can add gears is because I have a corvette with a tune that has eight gears and I didn’t know you could have eight gears… Any help is appreciated!

The number of gears over 6 is car specific. in other words only cars that come with more than 6 gears in real life have more than six in game. The only way to get more top speed for any car would be to upgrade the transmission and change the gear ratios in the upgrades and tuning section.