The gas tank on the 2005 Cadillac CTS holds 17 gal..
It means #7 cylinder is not firing properly. Could be a bad plug or plug wire on that cylinder.
You can find a 2003 Cadillac V-6 engine cooling system schematic diagram at most Cadillac dealerships. Many auto-parts stores will have the cooling system diagram.
The 2003 Cadillac CTS has a 5-speed manual.
You call a wagon wheel manufacturer by his name if it is advertised, or you already know his name, otherwise you would call the person Sir or Madam.
If you are asking, "What is the trade name of a wagon wheel manufacturer?
The answer is, "A wheelwright".