Pinstripe Potoroo is the fourth boss, racing on a modified version of Hot Air Skyway. His unique attack involves firing a machine gun.

Machine Gun Fire: Pinstripe will periodically stop his kart and fire his machine gun in a cone in front of him. If you're caught in the spray, you'll spin out.
Strategic Stops: He often stops in strategic locations, such as on straightaways or just before jumps, making it difficult to pass him safely.
Increased Frequency: As the race progresses, he'll fire his machine gun more frequently, requiring quicker reactions and more precise dodging.

Anticipate Firing: Learn to anticipate when he's about to stop and fire. Look for him to slow down slightly.
Quick Evasion: When he fires, quickly swerve out of his line of sight. This often means taking a wider line or hugging the opposite wall.
Hot Air Skyway Shortcut: The large jump shortcut on Hot Air Skyway is crucial. If you can consistently hit this, you can gain a significant lead and avoid many of his attacks.
Maintain Speed: Keep your mini-turbo chain going to maintain maximum speed and quickly get past him when he's vulnerable.
Shields for Protection: If you have a Shield, it can protect you from his machine gun fire, allowing you to drive straight through his attack.
Wumpa Fruit: Collect 10 Wumpa Fruits. Juiced-up offensive items are your best bet for hitting him and disrupting his firing pattern.

Defeating Pinstripe Potoroo unlocks the final boss challenge against Nitros Oxide, and grants you a Trophy.