Later on in the game around the second half, the enemy becomes very difficult, especially when determined. Nitro becomes an important weapon in your arsenal. What ever vehicle you use, having a upgraded nitrous kit is key to winning battles. Timing nitro usage is key to victory against powerful enemies and using it is a skill that is learned from playing often.
Nitrous Kits can be acquired from the Daily Nitrous Event; you can only acquire up to Grade 11 from the Extreme category.
Parts are obtained from Story rewards, CP Orders, Gold Orders and Order Tickets. It is also possible to obtain these parts from the 24 Hour Part Races.