you know what? IT really depends.
For outdoor parking lot racing this question would not even come up so i can only assume your racing indoors on carpet??
With CARPET racing the tracks are smaller and lanes are narrow. ITs not always easy for a slower car to find a spot to move over. With that said, if he is in your main that means he had the speed to make it in there with you. Either way if he is down 3 laps yes he is way off the pace wich should make it very easy to pass the guy when the right hole opens up. I notice alot of front runners come up on traffic and simply create there own headachs by not even letting up at all to compensate for the slower car. You know that everyone will have to pass this car so its not like the leader is the only one with the car to pass. A car thats 3 laps down should be dog slow on the straight, use that to pass him. A slow car will feel the pressure and make way eventually but dont expect the guy to just pull over and stop he is after all racing as well.
my 2cents worth