Volvo Repair: 2001 s80 codes, vacuum leaks, propane torch

Question
I have a 2001 s80 t6. The check engine light came on and I pulled codes 1171 and 1181. I cleared the codes and they came back a few days later. I have sprayed vacuum lines and intake with f/inj. cleaner to find vacuum leaks but have been unsuccesful. Car runs fine, just feels a little weaker at W.O.T. Any thought or advice? Im stumped and the dealer is an hour away. I'd really like to do the repair on my own. Thanks

Answer
  Travis, these can be tough. Be sure you check the injector o-rings and intake manifold gaskets for leaking. Then Check the exhaust for leaks.
   After that, you need a dual channel labscope to look at and compare the waveforms of both sensors in that bank. Pre and post. You want to look for slow or lazy signal response and proper voltages. First, introduce a large vacuum leak, Pull off a hose and watch the sensors respond. Then, introduce a rich condition, I like an unlit propane torch the best myself, and again observe the reaction/response time. The difference between the two sensors readings is going to indicate the health and ability of the catalytic convertor to convert hydrocarbons. that's the only way I know to be SURE what's really going on. Most shops sell you O2 sensors first and then go Huh?
   If all waveforms look normal , then you need to start looking at injector waveforms and millisecond on times to see if the problem is pre combustion and not post. Make sense? Air mass meters can be a problem, but usually the item of last resort. HTH.

Mark