Detonation?

[boogman20]

Hey, newb here. I put about 35k a year on a car in sales so I recently went back to the tried and true Honda brand. I recently purchased a 2001 Accord V-6 loaded, if you can say that.

 

Anyway, the car is VERY clean and pretty much female driven. I even had to get the EGR done at 78k (female driven, no offense). I am in tune with any vehicle I drive since I am in the car an average of 3 hours a day.

 

Here is my issue/question... Once I get the car in high gear with the converter locked up; if I ease on the gas while cruising at highway or any speed (as long as the converter will stay locked up) I hear light spark knock or valve rattle. Anyone have an issue with this? I know Honda says the plugs are good for 100k, but I'm at 80k and am thinking about changing them. Would older plugs contribute to this.

 

The car is getting decent mileage, but not as good as I anticipated. What should the mileage on this car be? Is 28 mpg highway unreasonable?

 

Thanks