I want to thank all of you who chime in here. I probably know more about my diesel than most of these "Kmart" mechanics out here. Again thanks for all your input and wisdom (even though it might sometimes come from mistakes we make)!!! I was doing a search for a miracle. Low and behold, I got to reading this thread. It so happens I have a 1985 300SD with over 200K on the odometer. I always thought the same things the mechanics say....Its a diesel...it has to be slow. But it got to a point where I also felt the low acceleration was a driving hazard and I was asking for a major accident if I did not look into what was going on. So, after reading some threads here, I did as some of you suggested...I bypassed the switchover valve and WOW!!!! my car is back to life. I started laughin when she took off becasue it was like a rocket. As I inspected further, I noticed the line coming from the manifold to the switchover valve is pretty cruddy, so cleaned the banjo bolt, cleaned the line, cleaned the switchover valve and the banjo bolt at the ALDA (I finally know what it is and what is does YIPEE) all with brake parts cleaner. When I put everything back together and reconnected the lines to the switchover valve...low and behold I was back to turttle land. I puched the accelerator....NOTHING! So I got out and bypassed the switchover valve again....and Yup, she was a rocket once again. My question, however, is...I only have when I was taking the switchover valve out to clean it, I noticed that there are only two lines coming from it..one over the top of the switch from the banjo at the manifold, and the one, also from the top, but protruding out going to the ALDA. There is also another orifice one on the bottom of the switch, but nothing attached to it. I scanned to see if there was a hanging vaccum line somewhere, but found nothing. Is this supposed to be this way, or is there something needing o be attached to it. Also, is this why my car losses power when connected to the switchover valve? Please help!!!