Repaired and have new problem

[Anemone]

Hi I have a 06' pontiac vibe FW AT Base. I had a p0171 check engine code showing, and got air wouldn't blow unless going at higher speeds. First i cleaned, but ended up replacing mass airflow intake sensor. Wasn't it. Took it to a shop they said: new radiator, water pump, radiator cap, and thermostat. Took it home replaced the parts myself and the drivebelt because it was cracking when I took it off. Reassembled and all of that worked fine with that part of it, and heating was much better, but then car died while driving first test run. This was not an issue before at all. So i took it to autozone, and alternator came back as fail in charging test. So i got new alternator and replaced it, and took it for another short drive and it happened again. While driving it dies, not stopped, and car will start again. Luckily I wasn't somewhere busy or upper speed limits. Voltage reads good with new alternator also.
So I have a few ponderings:
-My battery has slight play on the holding plate I usually have something shoved beside it securing it better, and maybe after taking off and putting on terminals it got touchy?
One time I was turning, and the other after driving through a roads dip to direct curb water thru road.
-My battery tests fine but could it need to be replaced?
-The alternator mounting bolts are not contacting properly? I did torque 40 lower and 18 upper ft lb, but that 18 is brutal to use a torque wrench and fit so I feel like it may not be 100% or cross threaded a bit?
-The alternator wiring is messed up from the uninstall/install? Everything is connected like before.
-The new drivebelt is effecting something? It's on right and lined up in proper grooves.
-Or tensioner pulley changed from drivebelt replacement and having to disengage and engage for belt install?
Anyways I don't have a huge knowledge base on these things, just how to do some repairs when needed and figure them out.
Any ideas or troubleshooting recommends would be really appreciated!

[VIBIN5spd]

Hang on.... p0171 is a lean code. Is this code still pending in your ECM? CEL on?

[JackWade]

I fixed my p0171 by replacing the air intake manifold gasket. Common problem and very easy to fix.