1974 Saw The Introduction Of US Required Impact Bumpers In The 911. These Bumpers Were So Successfully Integrated Into The Design That They Remained Unchanged For 15yrs. The Engine Was Also Fitted With K-Jetronic And Increased To 2,687cc, Giving More Torque. The 911 And 911S Models Had Detuned Versions Of The RS Engine, Producing 150 And 175 Bhp Respectively.