It depends on the crowd and what you're trying to sell them. I imagine the resistance is due to the fact they may not be able to hear the sells pitch, if you're revving your engine's throttle. Unless you're selling something that pertains to motorized bicycles; I wouldn't crank my bike up. Then whatever you're trying to peddle, the crowd should be better able to hear your sells pitch; thus offering up less resistance to you.
I understand steal or steel; brake or break lol. I've had people say they wanted a steal frame; I told them they better not steal mine. I also tell them brakes on a frame is a good thing but breaks on a frame is a bad thing.
Are you getting the resistance on level ground under no throttle or is it when you encounter climbing hills?