30bird wrote:Wondering if it might be easier to swap in
the 25317628 2001-2007 injectors for
the stock 25317669, 25320287 - 1999 injectors
Wha'd do you think would that solve my issue? will they even fit?
Truck injectors should be the same height and have the same connector, so they should be a direct swap.
Since you are throwing the P0171 and the P0174 codes, that tells me that your Long Term Fuel Trims (LTFT) are +23 or more, they actually max out at +25, so you are not commanding enough fuel. When I finish with a tune I like to see the LTFTs settle between 0 and -5. Short Term Fuel Trims (STFT) will always bounce around, because that is what the O2 sensors are doing. It's the average of the STFTs that determine the LTFTs values. We know that your LTFTs are probably maxed out, what are your STFTs values? The final fuel adjustment will be STFT + LTFT, so if your LTFTs are at +25 and your STFTs are +10, that would mean that the PCM is adjusting the fuel by +35.
You can tune by just using the stock O2 sensors and fuel trims, but keep in mind that you will not have valid data for when you are in open loop, such as warm up (usually below 131 deg. F ECT) and Power Enrichment (when you got your foot down). There are tutorials where you can log with PCM Logger, take that data and export it to a *.csv file and then export it to a program such as MegalogViewer to create charts where you can see what the fuel error is and then make changes to your VE and MAF tables.
Comparing the 1999 and 2002 tunes, the MAF tables are identical, but there are differences in the VE tables. I would try and get the PCM in "pure" MAF mode and see if the VE table is causing your issues. You can do that pretty easily by changing parameter B0120 - Dynamic Airflow Max RPM Threshold" from 4000 RPM to 100 RPM. From the factory the PCM runs a blend of VE and MAF up to 4000 RPM after which only the MAF is looked at for fueling. By lowering this value to 100 RPM we are basically telling the computer to ignore the VE table and use only the MAF for airflow calculations.
I would give that a shot and see if anything changes.