RE:injectors - accepting that the resistance is good, how did they spray? fog of mist, jet streams or?
valves getting recessed is something known on 4.0L's if I remember right... I have no idea how common it is in 3.0L's. If you had valves that weren't closing due to recess you would be getting misfire codes too. The 4.0's/2.9' (cologne block) have nothing in common with the 3.0's (vulcan block) - so issues common to the 2.9 (head cracking) are almost non-existent on the 3.0's
A leakdown test will show you the valves. Unless you love tearing into the engine and replacing gaskets I would do a leakdown before opening it up.
A systematic look at what those 3 codes have in common:
P0171:
P0175:
- Faulty oxygen sensor
- Clogged fuel injectors
- Fuel pressure regulator issues
- Vacuum leaks in the intake system
- Malfunctioning mass airflow sensor
P1152: (I had to look this one up - not ran into it)
- Faulty upstream heated oxygen sensor bank 2
- Air leaks after the MAF or PCV or between them, which would cause a lean condition resulting in Rich Bank 2.
- Bad MAF sensor
- Faulty fuel pump
- Lack of Upstream heated Oxygen Sensor Switch Sensor Indicates Rich Bank 2.
- Bad PCM (less likely)
- Vacuum leak on engine
Well as you can see all 3 have a bad O2 sensor on their list, that is the most likely in my books. Your aftermarket new O2 sensor could be like your 1 bad new injector - crappy aftermarket junk.
MAF shows up on all 3 lists... I've re-read 3 times now trying to get a good handle and I can't remember by the time I get to the post screen - where are we on MAF, cleaned the old, installed new?
There's something else that has to be on all 3 lists and you already said "the harness is lousy" - this all could be a wiring nightmare. I've never had to deal with any wiring problems other than breaks/cracks.... benefit of living in the desert (but at 30 years in the desert all plastic,rubber, wiring insulation is just about done - you only touch what you absolutely have to, and plan on replacing everything you touch...)