Hey guys, new to the forum and desperately looking for some help. I started my tahoe as usual today and noticed that it was missing pretty severely as I started rolling. So I pulled out my code reader, and the first thing that came up was a Random/Multiple Misfire Detected code. So my first instinct was to replace spark plugs and wires because the tahoe has 172,000 miles on it and haven't been replaced since I've owned it. Not sure how long the old set had been in there. That didn't fix the issue. So stumped, I did a little more research as after changing plugs and wires, the code changed from a Random/Multiple to a Cylinder 6 Misfire, O2 Sensor B2S1, and Sensor Reference code. So thinking that the upstream O2 sensor could have something to do with it, I went ahead and replaced both upstream O2 sensors. Since replacing them, it runs much better. It still starts rough, and seems to stutter occasionally at low RPM but seems to be fine under load or at RPM above 1500. At this point I'm completely stumped. Here are the codes it's still throwing: P0101 - Mass Air Flow Circuit Range/Performance (MAF is only a few weeks old) P0161 - O2 Sensor Heater Circuit Malfunction Bank 2 Sensor 2 P0641 - Sensor Reference Voltage A Circuit Open It's also worth mentioning that I have the codes P0327 and P0332 hanging around, which relate to knock sensors. I plan on replacing them soon, but from everything I've been told and read, these shouldn't be affecting my performance. They've thrown a light since I got the vehicle and have never affected performance. At this point I'm completely stumped as to what the source is. I've dropped over $200 now in parts to fix something and it isn't even completely fixed yet. So PLEASE provide any help you can. I need it. Thanks guys!