Does that small plugin device that you can place iunder the dash really work?? Do you sell them ND HOW MUCH ARE THEY.

They are basic, one from Harbor Freight or Amazon would be better in my opinion....

They work for a very limited diagnosis and error codes, but what is the issue with the car? Do you want to improve performance or just diagnose an issue?? :)

Yes, the OBD2 scanners do work, but I would recommend looking on Amazon.

I'm not sure what you are talking about