An engine modification can increase the speed of your electric or gas-powered golf cart. For electric carts, there are options like speed and torque conversion kits, more powerful motors, gear sets, and traction control systems. For a gas-powered cart, there are options like modifications for the clutch, traction control, and gear sets. You can spend a small amount (under $100) or a large amount (over $1000) to customize the power and speed of your golf cart.