Swap it with another and see if the miss moves. If so, you know what it is.
BTW it's not a bad idea to replace them as a set if you find that one is bad.
just a thought.

 

swapping the injectors is not as easy as the coil packs. I dont think the o rings can be reused Agree that all injectors should be changed together

 

Start the engine then pull fuel pump fuse #13 let engine stop from no fuel, turn off the ignition key. Change the injectors, orings and insulator cups and wash out the fuel injector rail with brake parts cleaner spray , it works great. Put it back together reinstall the fuse and prime the fuel pump, then start it up.

 

Which injectors should I get? They range in price from cheap to expensive. And many different brands A/C Delco, Sorensen, etc

By the way, I just checked and got a new code I never had before-PO106-manifold absolute pressure It happened after I accelerated hard, and the engine was sputtering a lot.

Could my MAP sensor be causing these problems? And even though I cleaned the MAF again, it is pretty old-could it be beyond cleaning bad?

 

Check the air horn connection between the MAF and the throttle body a loose clamp or crack in the rubber elbow

I recommend AC Delco injectors new , not refurbished . I have cleaned out injectors with carb cleaner , hooked up a 9 volt battery to open the injector and sprayed the cleaner through in both directions. 2 years now and still going great.

 

What did #2 spark plug look like? Clean, black, tan, orange. Different from the others?
Did you check the EVAP purge valve? It should be normally closed.
Coolant disappearing?
Cylinder compression test?

 

Finally installed the new AC/Delco injectors. For 2 days, no codes Then got the old PO171 again Cleared it and so far so good But the engine is still sounding raspy-it has sounded this way since the new cat/flex pipe installed.

 

Possibly the manifold to down pipe gasket? Try tightening up the fasteners . Look at the joint with the 2 fasteners is that gasket good and sealed? Tighten those bolts up .

 

Just changed plugs but old ones looked fine. But noticed that the PCV hose has a small crack by the valve cover. Going to replace it

By the way, before changing the fuel injectors, I would get the PO171 code within minutes after resetting the codes. With the new injectors, I can drive for hours, even days, without getting the code. Then it suddenly pops on. But the car is running notcibly smoother and better with the new injectors. And it took under 30 minutes

 

Those aren’t the correct plugs.
The cracked hose could be the source of your P0171 code.