When Volkswagen first debuted the new-for-2011 Jetta sedan, we were told that a total of four engine choices would be available. The standard Jetta makes use of the naturally aspirated 2.0- and 2.5-liter mills, as well as the much-loved 2.0-liter TDI powerplant. The final engine in this set - Volkswagen's turbocharged 2.0-liter four - now makes its debut under the hood of the 2012 Jetta GLI, which gets its official reveal at…