To limit power, all forced induction cars were fitted with a 34 mm diameter air restrictor before the turbocharger inlet, limiting the air flow to about 10 cubic meters per minute. The restriction was intended to limit power output to 300 hp although some WRC engines were believed to produce around 330–340 hp. Engine development did not focus on peak power output but towards producing a very wide powerband (or power curve). Typically, power output in excess of 300 hp was available from 3000 rpm to the 7500 rpm maximum, with a peak of 330–340 hp at around 5500 rpm. At 2000 rpm (the engine idle speed in "stage" mode) power output was slightly above 200 hp.
In an attempt to cut costs, since 2006 new regulations required mechanical front and rear differentials, while the central differential remained active. Active suspension and water injections were also prohibited. Cars entered by a manufacturer had to be equipped with the same engine for two rallies; further limitations were imposed on the changing of some parts, including suspension, steering, turbochargers and gearboxes.
His first WRC event was the 1987 Swedish Rally behind the wheel of his Nova, and again two years later, driving the Sierra and finishing 15th overall. Later that year, he finished 5th overall at Rally New Zealand in a rear wheel drive Sierra Cosworth. By 1990 McRae was driving a Sierra Cosworth 4x4 and achieved sixth place in that year's RAC Rally, despite several accidents. 1991 saw McRae turn professional as he was signed by Prodrive boss David Richards to his Subaru team in the British Rally Championship for an annual wage of approximately £10,000. McRae was British Rally Champion in both 1991 and 1992, soon graduating to the Subaru factory team at World Rally Championship level. 1992 also saw Colin McRae make his début in the British Touring Car Championship, with a one-off appearance for the Prodrive-run BMW factory team at the Knockhill round. In the second of the two races of the event, McRae collided with Matt Neal. Race officials found McRae to have caused an avoidable collision and subsequently disqualified him.
Most of the works drivers of the 1950s were amateurs, paid little or nothing, reimbursed their expenses and given bonuses for winning (although there were certainly exceptions, such as the Grand Prix drivers who were brought in for some events). Then in 1960 came arguably the first rallying superstar (and one of the first to be paid to rally full-time), Sweden's Erik Carlsson, driving for Saab.