Beginning with MY2004 however, production was outsourced to Valmet facilities in Spain, France, and Austria, and all subsequent road-legal Mezger engines are part-numbered "996.." (even 997 Generation).

This option replaced the standard electrically adjustable leather front seats with manually adjustable racing bucket seats finished in fire-retardant fabric, single mass flywheel, bolt-in half-roll cage, 6-point drivers racing harness (also replacing the standard side airbags), fire extinguisher (mounted in the front passenger footwell) and preparation for a battery master switch.

The muscular-looking rear end conceals a wider track that not only improves directional stability but also increases the potential cornering grip.

The US version of the 997 GT3 RS has a standard rear window (not plexiglas) and the smaller 911 fuel tank to comply with rules of SCCA, Can-Am, and IMSA.

It also featured a number of new options including dynamic engine mounts and a pneumatically lifting front axle to compensate for the low ground clearance.

[17][18] Porsche test drivers had intended[19] to enter the 2011 12 Hours of Nürburgring on a standard road legal 911 GT3 RS, but had to withdraw for health reasons from the team that comprised racers Roland Asch and Patrick Simon, plus journalists Horst von Saurma and Chris Harris.

[31] The 991 GT3 features a new 3.8 litre multi-point electronic indirect injection flat-six engine developing 349 kW; 469 hp (475 PS) at 8,250 rpm, a Porsche Doppelkupplung (PDK) double-clutch gearbox and rear-wheel steering.

[37] Subsequently, all 785 of the GT3s that had been produced up to that point were recalled to the dealership organisations and fitted with new engines, and all owners were issued with an extra year's warranty.

According to Dr. Walliser the concerning high-RPM misfire issue could be traced primarily to a metallurgical defect in certain batches of "finger followers" (valve train rocker arms) and secondarily to individual driving patterns and engine variations – such as temperature, oil quality, oil viscosity and parts tolerances – that lead to increased wear of the specific parts.

The 991 GT3 RS also comes with functions such as declutching by "paddle neutral" — comparable to pressing the clutch with a conventional manual gearbox — and Pit Speed limiter button.

A Weissach package including additional carbon fibre body and interior parts as well as magnesium wheels made by BBS and stiffer suspension settings is available as an option.

A steel roll cage was welded into the body and the car was fitted with an air-jack system, fire extinguisher and racing seat with safety harness.

[71][72] The suspension was similar to the GT3 road car in principle, but with variable springs, adjustable shocks, anti-roll bars and spherical joints.

[73] The 3.6-litre engine (Type M96/77) developed 302 kW (411 PS; 405 hp) at 8,200rpm when fitted with a 43.1 mm air restrictor plate, thereby meeting class regulations.

Other engine modifications included titanium conrods and valves, a racing exhaust system, as well as a dry-sump lubrication with an oil-water heat exchanger.

[76][77] The 2001 996 GT3 RS won the GTO Class in the 2001 British GT Championship at the hands of Parr Motorsport's Kelvin Burt and Marino Franchitti with 109 points.

Engine output was increased to 280 kW (381 PS; 375 hp) and 380 N⋅m (280 lbf⋅ft) of torque, further changes include improved transmission cooling, a lightened exhaust system and other light-weighing measures across the car.

The RSR featured ZF-Sachs shock absorbers which have Through-Rod-System with considerably lower chamber pressure and hence generate less friction than conventional dampers.

[90][91] Replacing the GT3 Cup S and built from the ground up for FIA GT3 regulations the GT3 R features a 4.0 litre, 368 kW (500 PS; 493 hp) boxer engine, a six-speed sequential transmission, a throttle-blip function, ABS and traction control.

The hybrid technology featured in the car was developed by the Williams F1 Team and is based on their F1 kinetic energy recovery system (KERS) which they did not race in 2009.

It uses lightweight materials in its construction, and a stripped-out cabin complete with a full roll cage, racing seat and all the safety gear required for competition, weighing 1,175 kg (2,590 lb).

Manthey Racing was chosen to run the cars in the FIA World Endurance Championship; the team achieved its best success at the 2013 24 Hours of Le Mans where the 991 RSR finished 1–2 in the GT class.

The car has a rear mid-engined design, powered by a 4.0-litre flat-six boxer engine, rated at 375 kW (510 PS; 503 hp) depending on series air restrictor.

Other new features include a new transmission, a new direct fuel injection, a new aerodynamic pack including a swan-neck wing and a larger rear diffuser, quick-change body panels and double-wishbone suspension with quick-change shim-system all around, Bertrandt-developed LED lights first developed for the 919 Hybrid and new cockpit with fixed seat, movable pedal box, multi-function steering wheel with integrated display, a rear-view camera and collision avoidance system.

[107][108] At the 2018 24 Hours of Le Mans the Manthey Racing-entered Porsche GT Team 911 RSR #92 and #91 finished 1–2 in the LM GTE Pro class respectively.

Improvements include a larger diffuser for more efficient aero, double wishbone front suspension adopted from the RSR, a shim system allowing setup changes without new alignment, larger front tyres, an electro-hydraulically actuated clutch allowing the removal of the clutch pedal, a fuel cell that can be configured to be refilled from left or right of the vehicle depending on circuit layout, a rear-view camera and collision avoidance system, a fixed seat with movable pedal-box and energy-absorbing impact elements placed in the doors for improved safety as well as air conditioning.

The car retains safety features such as a removable roof hatch and a rigidly-mounted seat with movable pedal-box from the predecessor model along with additional impact protection elements.

In the summer of 2022, Porsche unveiled the 992 generation of the 911 GT3 R. The car featured a bigger engine compared to its predecessor, producing up to 421 kW (565 bhp).

Due to the absence of the official Porsche team in the 1999 24 Hours of Le Mans, only privateers with the nearly obsolete air-cooled 993 GT2 Turbo were expected to represent the marque, with few chances to beat the Chrysler Viper for GTS class honors.

In the 24 Hours Nürburgring of the year 2000, a factory-backed effort of the local Phoenix team managed to beat the Zakspeed Chrysler Viper that dominated this race from 1998 to 2000.