p0171 and just got my engine replaced
 

Engine running too lean. I just got my inspection and everything passed except the emissions because of this code. If it's not one thing, it's another with this car recently. All whining aside, could it be my exhaust? Besides that, I can't think of anything. The engine just got replaced like 5k miles ago!

Most likely a vac leak :) Check your VFAD nipple...it will throw a lean code very quickly with it unplugged :)

I want to start buy saying rx8 solder that was awesome.. and you link should be a sticky. Isekiies the same thing happened to me. A few hundred miles after iI got my new engine and Mazda ran fuel enjector cleaner through my engine a couple times then ended up changing both of my o2 censors before they got it fixed, but now my cats goin out.