2010 HHR w/128K miles Flex/Fuel well kept and garaged

Had it 13-years and always been solid, until lately.

Stubborn P0172 code.

LFT is around -20 (way too high)
SFT fluctuates from -3/3 (give or take a few)
Alcohol content is 48% (gotten Phillips 66 gas at same station for years). E85 used once back in 2012 but none since then.

Chugs when first started with the occassional smell of gas.

What's been done so far and new parts (mostly AC Delco).

MAF sensor
both O2 sensors
air filter
plugs/coil packs
top EVAP valve
oil change

Reset to factory specs and blanked by removing both battery cables for 15-minutes, then clamping them together for 15-minutes. Seemed to zero out everything but the alcohol content. Still runs kind of rough with a shaky idle and a noticeable hesitation at higher speeds. Also notice that the engine taps way more than it used to before the light started showing up. Which, doesn't really make sense to me.

Any thoughts?

 

You clamped the Positive and Negative battery cables together ?
Uh Oh.

 

Sounds like fuel pump. Check the pressure and retention. Then check for vacuum leaks, especially around the EVAP purge valve the valve is Normally Closed in failure they usually stick open causing a hard start from too much air and gas fumes
When the CEL lights up the computer goes open loop, the engine is running with no feedback thus odd noises etc.

 

I suggest you remove the valve cover and inspect the timing chain for slack.
inspect the fuel lines front back for corrosion.
What prompted you to change all those parts? Codes? Parts counter person?