Whichever dealer did that to you should be taken to court. Assumption of modification is not a valid basis for warranty dismissal. I went through a case with my local Pontiac dealership dealing with this exact type of circumstance on my WS6. They tried to void my warranty because I kept blowing head gaskets, of course one of their genius bean counters AKA Service Manager, incorrectly assumed that the reason for this was Nitrous, and promptly refused. Needless to say he no proof to back it up, and after litigation i received a healthy settlement as well as full replacement of my parts. Unusual wear and tear is not always indicative of abuse, sometimes it is parts failure; as far as the unusually clean piston surface, TOP ENGINE CLEANER, produces almost the exact results. Now having said that, there are ways against tell tale markers in the diagnostics. Shift points do not change with nitrous,nor does shift pressure, occasionally (mainly due to poor nozzle placement) airflow values are high and IAT readings are low, but all of that can be changed by a preemptive re-flash of the ECM. However, if someone is inexperienced enough to leave anything "hardware" for the dealer to find in the first place, thats just Darwinism at work. Since the WS6 incident mentioned earlier, which by the way was a warped block not N2O as assumed, i have installed kits onto 3 personal vehicles, as well as 4 customer vehicles, with only one mishap due to faulty fuel. During the repair, under warranty, of the vehicle, not a single eyebrow was raised or question asked. Safe amounts of nitrous do no more damage to an engine than any other equivalent form of power increase. Nitrous doesn't hurt engines, dummies who cannot tune it do