Read this & this is indeed a special setup as what you're describing is a S197 that has a PCM that is set up to use Speed Density (a MAP sensor mounted on intake manifold DS of the supercharger to calculate air mass volume inside it) instead of a MAF sensor (MAF sensor mounted on MAF section just aft of the air filter & ahead of the TB to measure\calculate air mass flowing across it). So there wouldn't necessarily be a MAF sensor installed but both can co-exist on the same platform as well. FWIW, my FR Performance Intake Manifold on my 4.6L 3V has a mount for a MAP sensor molded into it...just not drilled out so running these 4.6L 3V engines using Speed Density thru a Spanish Oaks PCM is possible (have also looked at sample tune files thru HPTuners & have seen the settings\setup for Speed Density in there so it's possible).
Question, does the car start, idle, run & drive fine outside of getting the P0171 DTC? The focus should be directed as Macman45 has typed towards B1 due to the set DTC, which doesn't leave a lot of items to check for. But the 1 thing I would suggest is for you to use a scan tool that can display live data to then check the running FT's data when the PCM goes into CL to verify the P0171 DTC...both B1 STFT & B1 LTFT should be showing a much higher +% reading relative to B2 STFT & B2 LTFT. The reason why to check the live data is that you may have both B1 & B2 FT's showing high +% numbers but the PCM flagged\set B1 P0171 DTC due to it being a little higher thus closer to the threshold than B2 so the real issue may very well be across both banks.....the P0174 DTC code (B2) may still be pending instead of set.....you gotta think as the PCM "thinks" to make sense.....why it's always smart w\ these modern vehicles to check all codes (both pending & set) & live data either thru a scan tool or thru a datalog file to verify the actual issue(s) before going further to prevent unnecessary actions which will cause unneeded costs & frustrations when diagnosing these modern vehicles. Also is a good idea to check the Mode 6 data (the PCM self-check component test results data...especially the misfire monitor data) to see if the PCM is showing any cylinder "misfiring" on any\all B1 cylinders relative to B2 cylinders (if B1 cylinders are truly running lean the CKP sensor velocity pulses will be weaker & can show up as cylinder misfires relative to the B2 cylinders....another clue to help chase down the cause....if the MM is still enabled in the tune that is.... a cylinder doesn't have to be actually misfiring for the PCM to think it is a misfire due to the PCM using the CKP sensor signal to read CKP rotational velocity increases from a cylinder during it's power stroke to determine if a cylinder is firing\misfiring...incomplete combustion from an overly lean mixture can cause the same CKP signal effect as a real misfire....so you can pull coils\spark plugs & find nothing wrong w\ them).
Now you may have done all this already.....but we can't tell thru the info that is posted...………… Also what I've posted the ROUSH folks should have asked for any evidence of pending DTC's before saying what they said.....can be misleading...……
Just saying...……..
If SD & a vacuum leak is manifold related the engine idle speed usually increases due to the O2 sensors picking up the extra, unburnt O2 in exhaust that the MAP sensor can't pick up\measure due to no measurable change in intake manifold pressure post SC rotors (SC bypass valve is open during idle so no boost\positive pressure, only vacuum) thus why the original question I asked as to how the car is running, especially at idle....unless the actual leak is located on 1 (or more) of the individual intake runners at the intake\head mounting on B1. This is where I would recommend to get the intake system smoke tested for vacuum leaks as you said the key word...obvious.... Since this engine is SC'd there are more areas for a vacuum leak to appear than you may realize & this issue is most likely occurring only during idle. Also need to look at the O2 sensor's voltage output to see if they're operating properly.
Would be even better to datalog\use scan tool to look at data thru a full cold start thru to full hot idle (to view data transition from OL to CL to cover all the bases as if any vacuum leaks are present they're more easily found while the engine is cold vs when it is hot (thus the recommendation to perform smoke test on cold engine to verify\rule out vacuum leaks) & the FT data can help flag this during the transition from OL to CL when the O2 sensors start reporting to the PCM so the PCM starts controlling the fueling according to AFR setting instead of using OL fuel settings from the OL base cold fuel map. If the O2 sensors spike high +% STFT numbers right off the bat (they should go -% STFT numbers due to OL cold start fuel enrichment being applied) you have extra air in the system than what is calculated...a vacuum leak(s), short fuel delivery or MAP related issue....another way to verify a potential vacuum leak w\o having to do anything extra except read a scan tool\datalog…….
Sorry for the long posting but since you did say that you wanted to verify these issues yourself before you take it anywhere then you really need to get a good scan tool that can allow reading of the live data stream AND access to the PCM stored Mode 6 test results data. Any shop worth their salt is gonna do exactly what I've posted....for a shop rate of at least min 1hr labor time @ $85.00\hr-$120.00\hr but a good, decent scan tool will cost you less...some much less.
Hope this helps.
