I just put a new K&N intake (pt.#77-2570KTK) on my 6.8 Lt. '01 E-350 SD today. This has to be the easiest hp upgrade short of a plug in programmer. The instructions were clear and well written. Working time was only 35 minutes. K&N claims approx. 17+ hp increase. I don't have access to a dyno, but when I went out for a test ride, I do believe that I felt a difference in seat of my pants. I definitely heard a difference. I'm going on a trip this coming week and will be comparing the performance against past trips.