no acceleration...no top end...

[Gr8video]

Hi,
I've been searching the posts but haven't found my issue. I've got a 2001 E350 and was coming down the Grapevine (northbound) and it suddenly felt a bit funny. When I hit the flat I couldn't get past 60 and when I pulled off for fuel I could barely make it up the overpass. It took forever to get to 50mph...(maybe a full minute) idles rough and the "service engine" light is on...(not the "check engine" light) I changed the fuel filter and the air filters and was going to check the waste gate until I saw a post that told me the vans don't have a waste gate. Ideas?
Thanks in advance...