What can a restricted exhaust system lead to in an engine?

A restricted exhaust system can significantly impact an engine's performance, primarily leading to power loss. The exhaust system is responsible for expelling gases produced during combustion. When restriction occurs, it can cause back pressure to build up in the exhaust, making it more difficult for the engine to expel these gases efficiently.

As a result, the engine struggles to draw in fresh air and fuel, which can lead to reduced overall performance. Specifically, power loss happens because the engine can't breathe properly, which directly affects its ability to generate horsepower and torque. When back pressure is high due to a restriction, the engine may also experience reduced efficiency in combustion, further contributing to a decrease in power output.

The other options do not accurately reflect the consequences of a restricted exhaust system. Increased fuel efficiency and improved acceleration would generally be associated with an unobstructed exhaust that allows for optimal engine breathing, while lower emissions are more likely a result of proper engine operation rather than a restriction in the exhaust flow.