you will still need to replace the fuel pump to fix the lean code.

 

Just had this exact same problem on my 07 LT w/105,xxx miles. Replaced the fuel pump myself with one out of a salvage with 38,xxx (I know, probably not the best move, but only cost me $40). Not a hard process if you're a little mechanically inclined and have a jack and some stands and basic tools (15 mm socket, flathead screwdriver, hammer). Only took me about 1 1/2 hrs.

Not the ideal solution, but will work.

 

At 135K, your fuel pump is likely on borrowed time. A leaking fuel injector could also cause the pressure drop and decreased mileage but it should show up as a rich condition. Isn't there also a relief valve on the injector rail to return to the tank?

If you're planning on running the car to 200K, you might want to change pump and injectors.

 

The fuel psi regulator (relief valve) is built into the fuel pump assembly. The hhr uses a returnless fuel system. And yes if it had a leaky injector it would probabiliy have a rich code and cyl. misfire.

 

It was easy to change on the fuel rail. A little harder in the tank. Wish they would have access panels so you don't need to drop the tank.

 

That would be great. but in the end its all about the cost.