cheapassdiesel.com sells them for around 100 to 150 and they do work. I use one on a 2000 F 250 towing up to 12000 lbs.and it helps braking. Not like a full fledge exhuast brake but it will help slow you down. They say no harm when used. Just know your limtitaions. They also sell a torque...
I am new and I have a 2000 F250 I would like to know about a company called cheapassdiesel. Looking forward to joining in on the fun and learn something at the same time.