With rising costs and factory teams walking away from the series which meant diminishing entries, IMSA introduced a new prototype category for in 1993 called World Sport Car (WSC). The WSC replaced the GTP and Lights closed-top cars for the following year. The WSC cars were open-top, flat-bottomed sports-prototypes with production engine as opposed to racing versions of production engines from GTP cars. The main goal of the WSC introduction was to reduce the costs and bring back the private teams to the tracks, which had been kind of slashed down by the factories. The WSC cars made their debut at the Miami Grand Prix with a sole entry of Brent O'Neill. The car finished last among the cars that were still running. After skipping the 12 Hours of Sebring, the category would compete for the remainder of the season as non-championship rounds, with no more than four cars entering. In 1994 Camel would be replaced by Exxon as the title sponsor. However, as the WSC cars took over as the leading category, their reliability would be tested at the opening round at the 24 Hours of Daytona. Two cars started on the front row, with eight WSC cars competing. Two cars finished the race, with the leading WSC car finishing ninth behind GT cars. The WSC cars would score its first podium finish at Sebring with a second and third place behind a Daytona winning GTS category Nissan 300ZX. That led to a rule change for the latter category as they would be barred from using engines that were originally for GTP cars. At the inaugural round for WSC cars at Road Atlanta, the new Ferrari 333 SP would make its debut in a mass media fanfare and win its debut race. The car regularly appearing on the podium on every round after that. Oldsmobile won the manufacturer's title over Ferrari by four points. In 1995, a new rival for Ferrari appeared in the Riley & Scott Mk III. The car would make its debut at Daytona, but would retire after the eleventh lap after an engine failure. Ferrari would help the category to score an overall win at the 12 Hours of Sebring, and would take the title for both makes and driver. The Ferrari and the R&S cars were the dominant racers of the series from 1995 to the demise of IMSA at the end of 1998. In 1996 Slater sold the organization to Roberto Muller (ex-CEO of Reebok) and Wall Street financier Andy Evans, who also was an IndyCar owner and owner/driver of the Scandia WSC team. Evans and VP of Marketing Kurtis Eide were responsible for the name change to Professional Sports Car Racing (PSCR). In 1992, the long running category American Challenge would step into the GT series. It became known as the GTO category when the former GTO category was renamed to GTS (Grand Touring Supreme). The move was prompted by sponsor Exxon, who wanted the series named after its subbrand of fuel.[22] In 1995, in a bid to move close to the European BPR Global GT Series, the GT category would undergo another major reformat. GTS became known as GTS-1, and GTU became known as GTS-2. In 1997, there was another category addition. GTS-2 became GTS-3, new GTS-2 category was announced to allow for the existing GT2 cars.

Brent O'neill Argo JM19 Buick was converted to WSC specs in 1993.