How to Diagnosis a Rough Idle and Hesitation

Hi Everyone: This 2001 Hyundai Santa Fe with a 2.4L engine has a rough idle and hesitation. The code is PO171, system lean, freeze frame fuel trim is 12.5 %. At idle the fuel trim is minus 12.5% and at 2,500 rpm is 5.5%. The problem I found was air filter not installed properly allowing dirt to get sucked into the engine, the wrong spark plugs for the vehicle and a collapsed PVC hose. For more information be sure to visist: