992.1 Turbo Non-S/S 3.7L 74mm IPD Plenum ('20-Current)992 Turbo S Plenum The 992 Turbo engine is another modern marvel from Porsche. We were fortunate enough to have unlimited access to a 992 during our extensive development and testing program. This unrestricted time frame proved to be invaluable, allowing IPD to scrutinize every engineering and design aspect in an effort to deliver the best performing Plenum possible. Like all previous IPD Turbo Plenums, the 992 Plenum is a product of efficiency that