I have a Volvo 08 S80 v8 I changed the valve cover gasket and intake gasket about four days after driving the car, check engine light came on ,scanned it got codes p0171 and p0174. my short term fuel trim is around 0 to 9 and my long term is at 29 at idle. When ever I give it gas the long term drops down to 0. What else do i need to check to solve this problem ?

 

Check for intake air leaks, vacuum lines etc. Next check the air filter and intake itself. It also may be due to the O2 sensor (front?) if you don't find a leak or a restrictive filter..

 

Me and a friend did a smoke test on the intake. The front valve cover gasket is leaking. I would like to know if anyone has the sequence and torque specs.