well the subject is quite geeky but, i believe that a well adjusted PID would actually make for lost speed a litlle, oscillating when near the control point

Actually it could also be an adaptative controller ( laguerre polynomial based one for example). This kind of solution is quite accurate and adapts to every car (as long a measurement device is accurate) It is also quite light as it is just simple algebra (well maybe a bit too much for just using iram)
well there is just another more plausible solution : the highway spirit :-)