95% of the forced induction cars out there don't run Wideband set ups.
As stated....this is all monitored for you when you take the vehicle in for the tune. Is it a waste fo money? No. Can you run one? Sure....but is it a necessity? Nope...not if you're taking it in to be tuned anyway.
I mean...if that were the case, everyone should be running one. Forced induction, N/A, or otherwise. As far as your bad sensor goes....as much as you'd like to credit your wideband for finding it for you, you could have easily found that code by running a plain old diagnostic on it just the same.
I had the Innovate LM-1 set up on my Cougar. I bought it with the intention of doing my own tuning. When that didn't work out, I brought it to they dyno to have it done. They did a spot on job. About a year later, the wideband sensor burnt out and it started flashing error codes and quit working and I never used it again. I could have spend the $200 of something far more useful.
Again...if you're going to tune your own vehcile....by all means, buy it. If not...rely on the equipment at your local dyno. They make their living making sure that their stuff if accurate and working. Don't give it a second though.
Under that logic, there'd be no reason to run an oil pressure guage. Jiffy Lube did a fine job of changing that oil.
I mean... I was going to change the oil myself but one thing led to another and before you know it, I was on the rack at the 20 minute oil change so I didn't need that pressure guage anymore.
An over simplification to be sure. Regardless, if you're running a boosted and something happens... Anything... When do you suppose the best time to discover problem might be?
I cannot subscribe to the idea that if someone else tunes it, that, that is that. I've come across two separate occations where the wideband saved me the potential of thousands of dollars:
The first was when the distributor hold down worked it's way loose. The dizzy had rotated to the advance side and I noticed that the AFR was leaner than usual. A little more power to the accelerator confirmed that something was wrong. I get back to the house and pop the hood, looking for a vac leak or something obvious. Leaning over to look with my hand on the dizzy, uncovered the problem.
The second was a power shift that went wrong. Rev/Pop. Shortly after that was when I discovered (again) a lean condition. It took two seconds under the hood to see that the cross-over line between the boosted and non-boosted manifolds had popped off of the intake.
So there are two conditions that could have been catesrophic causing lean detonation circumstances under boost. Neither of those conditions would have revealed themselves from any other cockpit aid, other than Air Fuel Ratio.
Furthermore, how many dyno shops out there take the time to do part power tuning? Maybe half? Most do the WOT tuning and call it quits. It's pretty nice being able to produce a data log to take back to the tuner after some seat time and say, "Here... it's not right at part/full power between rpm x and y".
It also comes in handy when switching from this gas station or that. Most times, crappy or good gas can be compensated for with a minor timing adjustment (particularly on those cars (Fox) without knock sensors).
Ah... I failed to mention one other circumstance where the wideband helped with a diagnosis. It's a comon problem too. The chip in the back the EEC. They're NOTORIOUS for not seating correctly. There were other symptoms that went along with the problem but it becomes as plain as the nose on your face when your AFR looks like it did BEFORE you got your tune.
Dead giveaway.