What is one potential consequence of having an exhaust backpressure of more than 2.75 psi?

Having an exhaust backpressure of more than 2.75 psi can lead to increased emissions. This occurs because excessive backpressure in the exhaust system can hinder the efficient evacuation of exhaust gases from the engine. When exhaust gases are not expelled efficiently, the combustion process can become less effective, resulting in incomplete combustion. This, in turn, leads to the production of higher levels of harmful pollutants such as hydrocarbons and carbon monoxide, thus increasing the overall emissions from the vehicle.

In terms of vehicle performance, increased backpressure can negatively influence the engine's ability to take in fresh air and expel used air. Consequently, this disruption can also impact engine efficiency and fuel economy, as more fuel may be needed to maintain performance under conditions of increased backpressure. Although other answers involve certain concepts related to engine performance and efficiency, they do not align with the direct consequences of excessive exhaust backpressure as clearly as increased emissions does.