I just bought this one for the same exact reason, it removes under coating and removes heavy grease and grime quicker, easier, better than anything else I've tried. I contacted the local Hotsy rep and had him keep an eye out for a good used one for me, after a 4 month wait he found one (people tend to hang on to them so used are not always easy to find).

They retail new for about 5K but I got this one for $1,200.00 and it works awesome, it came with some extras like a new hose and hose reel, extension cord, etc. The specs are pretty basic, single phase power required, diesel or kerosene fuel for the burner, 1,500 psi sprayer, heat rating is 240 degrees F (but actually only heats to about 200).

I love this thing!