sentences:  The engine thus modified became the 'Merlin TMO' in contrast to the unmodified engine, the Merlin TML - Transport Merlin L. The modified exhaust conferred an increase in horsepower over the unmodified system of 38 hp, resulting in a 5 knot improvement in true air speed.Sound levels were reduced by between 5 and 8 decibels.Still air range of the aircraft was also improved by around 4 per cent.