Complex sentence: First fuel consumption and then turbocharger boost were restricted-to 4-bar in 1987 and 1.5-bar in 1988; by 1988 the turbos were only slightly more powerful than the lighter 3.5-litre naturally aspirated cars that had been introduced the previous year.
Split into simpler sentences: First fuel consumption and then turbocharger boost were restricted to 4-bar in 1987 and 1.5-bar in 1988. By 1988, the turbos were only slightly more powerful than the lighter 3.5-litre naturally aspirated cars that had been introduced the previous year.