UK Car Repair Questions? Ask a Mechanic for Answers ASAP
The codes P0171 and P0174 are lean codes which can cause the restricted performance. We need to make sure these fault codes are the ones that have returned. On the V6 engine I see some issues with vacuum leaks from the intake seals, IMT seals as well as vacuum hoses and connections. We also need to check the air intake tube. Other possibilities are a faulty mass air flow sensor or even a clogged fuel filter or weak pump. Start the engine cold and listen for any air or hissing noise form the engine. We also need to scan it again to confirm the faults. Let me know.