I apologise for the length. Good afternoon, I have a 2006 VW Jetta 2.5. My issue started when my alternator serpentine belt cracked in half lengthwise; I noticed issues with the idle to the point that I could take my foot off the gas, while in gear, and the car would keep going. I ran the OBDII scanner and got a bunch of codes about higher idle than normal, and system lean bank 1, and O2 sensor readings off. I replaced both belts, and went looking for a vac leak in all the soft hoses around the passenger side of the engine. I Found 1 cracked hose at the vapor canister purge valve, and I noticed the valve was off its post that it attaches to. So I replaced the vac line, and couldn't find any others. Still had the same codes, so I went ahead and replaced the valve that had gotten lashed by the belt, all of my codes have gone away except for P0171 and P0507. I've reset the ECU, and allowed the time necessary to relearn the idle. I recently did the, "hold the gas in, turn key on, hold for 10 sec. and then release and key off' trick. After doing this, the rpms hold steady between 12-14k. I've gone looking with smoke and starter fluid on all of the vac lines, no leaks. I cannot find any cracks in the manifold. MY PCV valve was fine, so unless a shard of belt hit it on the other side of the engine, I'm going to assume this is some electronic throttle relearning that has to be done. I've sprayed throttle body cleaner and wiped it down, but had not opened it and cleaned on the other side, because I don't want to mess up the TPS and all of that. What are your thoughts?