Toyota Repair: 1999 4runner emission problems!, throttle position sensor, mass air flow

Question
the code i got was a P0171 system too lean (bank 1)-------------------------
Followup To
Question -
Hey, I have a 1999 4runner V6 2wd 80,000 miles and been having problem with the check engine light. first i had a technician check it out and told me that the 02 sensors had to be changed. i had the 02 sensors changed and the following day, the light re-appeared. I took my truck back but this time he told me that the Mass Air Flow or the Throttle Position Sensor could be the problem and that there was no way of knowing. feeling i was ripped off, i had the toyota dealer have a look at it. they told me that the MAF needed change and that my fuel injectors needed cleaning. so i had both the MAF and TPS changed and added a can of BG 44k to clean the fuel injector system, but the damn check engine light came on again. as i need a smog check quickly, i was wondering if you might help with the problem im having?
i have spend over 400 to change the 02 sensor & A/f meter, 250 for the MAF, and 80 for the TPS plus all the labor!
please help me if you have any idea as to what the REAL problem might be!
thanks man!
Answer -
I have no idea unless you can give me the diagnostic trouble codes that were retreived when the repairs were done, or at least the ones that are stored in the computer at this time, please have a OBD scantool connected and let me know what the trouble codes are and I can probably help.

Answer
The P0171 lean condition/fuel trim code is always caused by the air flow meter unless there is another mechanical problem with the engine which I think may be the case here.
There are some possible causes for this:
There may be an engine misfire, id the 171 code the only code output or are there more, I'm thinking there could be an engine misfire but it would cause a misfire code or at least it should.
There may be an air leak in the intake system, a hose disconnected maybe.
I understand that the original trouble code was 171 but have you had it checked after the repairs were done, it is possible that now a different trouble code may exist, that is why I asked what the trouble code is at this time, after they replaced all that stuff.