991.1 Porsche Turbo / Turbo S IPD High Flow Y Pipe991 Turbo S IPD High Flow Y Pipe Part #91500 The latest 991 Turbo from Stuttgart is another milestone mechanical achievement that once again raises the performance bar to a level reserved for a very elite group of supercars. Ballistic acceleration and a top speed of just under 200 mph makes it the most powerful 911 based Turbo to date. But of course there is always room for performance improvements for Porsche driving enthusiasts looking to raise the