I hope I can make some sense here about what little I know about decibles.
Sound decibles are measured on (I think it's called) a logarithmic scale. 97 isn't a little louder than 95, it's a LOT. Distance and angle are important 10' will give you a much higher reading than 15'. If the pipes are angle cut, standing right behind will not be accurate. Sound measuring is like challenging the handheld police speed detectors used to be, and can be argued in court, if you have the time and money. Personally, I have found that anything less than open drag pipes ridden responsibly will not attract the attention that quieter pipes ridden agressively will.