[kach22i]

Modifying the mufflers on a Porsche twin turbo (993).
AutoSpeed - Porsche Power!

And what about power? Here the result was startlingly good - the modified mufflers found no less than 18hp, or a gain in peak power of just over 7 per cent.

http://www.autospeed.com/cms/A_112994/article.html?popularArticle

In the late 1940s a revolutionary new aircraft engine was developed, one that just stunned contemporary engineers. Developed for aircraft, the diesel two-stroke boasted 12 cylinders, a displacement of 41.1 litres – and developed up to 4,100 effective horsepower.