Im getting same 2 codes. P1171 has been around for awhile, Ill clear it then after a week or so it comes back, today both P1171 and a new code P1174 popped up. Ill still trying to track the causes for my fault codes. Good luck to you and let us know what you come up with.

 

After doing the cigar smoke test, mine was the push lock fitting on the intake manifold.

 

Mine ended up being caused by deteriorated injector o-rings. Figured it out after several vacuum leak test with brake kleen. Sprayed in the valley directly at injectors for 1,2,3,4 which you can see from top of engine and reach with a straw on the spray tip.