I guess the gap there is that the German manufacturers are proactively looking for a tune any time the car comes in, and they have taken that out of the techs hands to confirm.
With Lexus/Toyota they would be re-actively looking for a tune based on an engine/transmission failure...and that's not going to be done at the dealer level.
When you look at the lineup of vehicles that Toyota/Lexus sells, how many of them would you think there would be a tune for versus the German big 3 (Audi, BMW, MB).
Ain't nobody going to be tuning a Yaris or Sienna or Highlander or 4Runner (this list goes on and on)...or an ES, CT, RX, or likely even an LS.
I would say good candidates are FRS, Supra, IS F, IS350, GSF, RCF, maybe an LC, but that's even a stretch. LFA...I don't know if there's even enough of them to make it worth it to develop a tune.
The vast majority of cars that Toyota/Lexus build are not vehicles that anyone is going to want to tune. The cars that they did build that have been tuned out the ying yang are so old that they weren't even made this century...MR2, Corolla GTS, Supra, Celica GTS Turbo AWD, and probably a couple I'm missing.

I have a buddy that worked for Lexus and now works for Toyota...I'll ask him if he can tell if a car is tuned using the Techstream software.
Ironically I never asked him because I know they can't, but I'll make it official and ask him.
You are correct that they could give you misinformation for various reasons, but the Germans, Subaru, and Ford all admit they can detect tunes, so why not put it out there honestly.
That way the customers know not to bring the cars to the dealer, and the dealer doesn't have to deal with a headache when they tell the customer the engine warranty is void.
And really, because the IS has no forced induction there's only so much a proper tune can do, and it's not enough to blow anything up. Toyota/Lexus doesn't have a reputation of reliability for under-building car components.

 

All good points.

There is one major problem though. I walk to the dealer, buy an is300 (which let's say was tuned by the previous owner), and I experience problems (example, blown engine) a year later. Well, how will lexus prove it was me or the previous owner if they dont even check?? How can I, today, buy an is300 or is350, and make it was not flashed, before I even buy it?

 

Another question I have: if I buy another ECU from lexus (or get a used one on ebay) will it work with the immobilizer, vinyl, etc?

I know on german cars it's not posdible.

The idea is to buy a used ecu, tune it, and put back the original ECU when doing warranty. There is no way in hell the dealer can ever find out. Anyone tried that ?

 

In theory that would work. There is a "marrying" process that will need to be done every time you swap ECU's.
Additionally you'll need a Techstream to write the VIN into the ECU as well.
Since the original ECU will have the VIN, then you will only need to write it once into the new ECU.
You would have to make sure that the ECU has the same part number as well as the same engine and tranny calibration codes...basically the same version of software...that way it will appear like it's the same ECU.

 

Interesting.

So if I get an ECU from a donor car which has the same year, I believe it would work.

Can the whole process be done at home if I have Techstream and another ECU at hand, or it has to be done at the dealer (which would defeat the purpose)? Does not seem like it was done, at least not that I can find a How-To on it

 

Same year and same part number. There will be a few ECU part numbers for each year based on engine and tranny options.
You can do the entire process at home if you have a Techstream.
There are Youtube videos showing how to "marry" the ECU to the vehicle...it's the same process on the 2IS, but 2IS doesn't have the VIN write function...I don't think.
The process is actually pretty easy, you take a jumper wire and jump 2 terminals at the OBD II connector and then turn the Ignition on for 30 minutes...I can't remember the 2 terminals off hand.
The VIN write is just going in with the Techstream, selecting the option and type in the VIN...if you can read and write (pun intended), then it's straight forward LOL!

 

well if I go that route, I would buy a used ecu, so i can always ask the seller for the ecu part number. I really dont think lexus changed any engine or tranny on a awd is300 2016 for example. But it might be that for example an Fsport 2, versus a luxury package versus an fsport 3 might have a different ecu.

Anyway, the advantage of the 2016 over the 2017 is that I can keep the dongle with the 2016, and flash or put back to stock at will.

The 2017, I would have to keep the flash unit with me, which costs $500sh.

 

What I meant by same year and part number is that for model year 2016, there is the 200t, 300, 350...and in among those models there is RWD and AWD.
So that's 5 different ECU's...hence why the part number from yours will be needed to get the correct ECU. I'm sure there is only one ECU part number for 2016 300 AWD, but for something like this I wouldn't rely on an online parts catalog as there is so much room for error.
Just pull out your ECU and get the correct number off the label, then just look for the same number. It's possible the ECU could be used in other years as well, so best thing is to just look for the part number. The part number is king!

 

got it. thanks a lot.