Is your car tuned?

[cf105arrow]

I’ve had guys ask me if my car was tuned because of how nicely it runs. I bought my car as a resale from a dealer in 2012 (2009 Mustang GT). They never mentioned a tune and I didn’t receivd a tuner. I’ve been running regular fuel with no issues aside from a very rare rattle through 4000 rpm under high power. I tried running a higher octane fuel through the engine just in case it was a fuel issue but there was no change. I assumed the rattle was just something I couldn’t find.
I brought my car into Ford for an airbag recall recently and asked them to reset the speedometer because it has always been out by 5 km/h. I get a call later that day from the dealer later that day and they asked me if I tuned the car to which I answered no. They said they couldn’t reset the speedo because there is an existing tune. They would have to reset the computer back to stock if I wanted the change. “NO THANK YOU!” I replied.
I had an engine light come on recently even though the car runs the same (great). I assumed it was just a sensor. Decided to run Ultra 94 from PetroCanada. Within a hundred km the engine light went out and under heavy power I’ve yet to hear a rattle.
The point: get the dealer to check for a tune before you purchase. Thankfully I never experienced any problems but could have.

Any ideas as to why the engine light went out after running 94.

[Ponyryd]

Light may have went out unrelated to the fuel, tough to say without knowing the code.

[cf105arrow]

It’s a possibility but it was on for a while and the fuel type was the only factor that changed. Maybe the light burned out.

[Uncle Buck]

Toss a code reader on and see if there are any stored codes.