Need equipment to make critical measurements? Buy the cheapest shit you can find! It totally works, guys. No, seriously.
It's not exactly critical stuff...get it close with a wideband, read some plugs, call it good.
It is when your reputation is based off of it. When you want the car to perform it's best and not leave power on the table that could be safely made. When everyone has a fevered little fucking ego and makes pulling a fender on someone else into an episode of Jerry Springer, does the last 10 whp matter?
If Bosch sensors were so terrible, would OEMs run them? Would as many turbo cars still living today who've been tuned with them still be running? Get off your fucking measurement equipment high horse...
There is a vast difference between using a Bosch sensor to control closed loop operation, and tuning an engine with a Bosch sensor. The OEMs do not use Bosch sensors to tune with.
By your logic, if AEM widebands sucked nobody would buy them. Well they do suck, and technological illiterates line up to buy them. They are not merely inaccurate, but the Vout so unstable as to be completely unusable, and people continue to buy them in quantity. It's really funny when the dollar vs time to own an NTK based setup is break even for most enthusiasts, and Bosch sensors a fiscal loss for a part time street tuner after the second year... 4-6 months at a busy dyno shop and they are throwing money away.
"Ideal" AFR for a reasonably designed water jacketed motor is nominally 12:1, max cooling is 11.5:1 and any richer promotes misfires. The difference between a Bosch and NTK sensor is 0->1.5 points, with 1 to 1.5 points being average, in a reasonably well designed exhaust tract - this means no unusually high heat or pressure to skew the sensors, particularly the Bosch sensors that will not tolerate it. Too close to the heat source? Does the 3" exhaust neck down to 1.5" crush bent going over the rear axle a la Pigfucker? Guess how that shit reads.
I deal, every day, in practical applications where cost is THE biggest factor. I'm talking about buying $300 in gear, expecting it to last longer than any same type gear you've owned or your friends have owned, and have it make a noticeable impact on the quality of your tuning. I am not talking theory, or I saw it once or twice, or read about it on a forum and it's supposedly hot shit. I'm talking about I've owned more widebands than everyone else in this thread combined, I work with widebands for a living, and I've owned the current NTK rig for 3.5 years and I am impressed.
You don't want to listen? People like you make me look good.