Mods [removing builtin safeties] are fradulent in my opinion in that the odometer is supposed to reflect the internal conditions of vehicle components and things that over stress [nitrous, supercharging, etc] are not reflected via the odometer. Emission tampering is unlawful just as odometer tampering is a felony.

Buyers have a reasonable expectation of getting a 25k engine/tranny if the odometer shows 25k..............not if the internals are almost liquified by stresses.

However the used car business might collaspe if absolute truth was required.
It depends primarily on the mechanical ignorance of buyers.

 

This is going to become an academic debate and somewhat of a thread hijack, but there are other things that are not reflected via the odometer, which can impact the mechanical integrity and resale value of the car. Things such as the manner in which a car has been driven or cared for may impact the usable life of a car/engine.

I agree that the seller has an ethical responsibility to disclose modifications that had been done to the car, leaving the purchase decision to the potential buyer. I also believe that the buyer, especially a dealer, has a responsibility to test the mechanical integrity of the car and assess its value, but I do not agree with your general assessment that a turbo measurably shortens the usable life span of that car.

 

Based on oem [stock 300zxtt] turbo designs I would agree that turbos don't decrease the ultimate usable engine life more than say 50% from 300k down to 150k] depending upon number and time of wot usage!

I rarely see 300zxtt with more than 150k [without a rebuild] where I regularily see J30 with 300k and non turbos 300zx with higher mileage.

Many would be happy with 75-150k turboed mileage?

Aftermarket turbos without oil squirters and optimized pistons, cams, etc may be more agressive or not, probably less reliable than an oem design.

If turbos are limited to oem type low pressures little reason why they should be less robust than oem designed turbos. But we know aftermarket run >8psi boost.