The W5-GSTR went through a redesign in Gangstar Vegas. The current vehicle design, which is featured in the latest version of Vegas and every version of New Orleans, is based almost exclusively on the 2015 Mercedes-Benz CLS-Class. The original W5-GSTR, on the other hand, was modeled on a number of different vehicles including the Ford Taurus and the Mercedes-Benz E-Class.
For unknown reasons, W5-GSTR in Gangstar: New Orleans received new rims during updates.
The vehicles can be found in any affluent area of the map, especially the residential districts of Kenner and Metairie. Unsurprisingly, W5-GSTRs serves as non-player character (NPC) vehicles for most street races in both games.
The vehicle's engine sounds like a V8 in Gangstar Vegas if the player stops and idles the car. Anomalously, New Orleans' version of the W5-GSTR sounds far more like an in-line four-cylinder engine.