forgot to add this you need to check your exhaust backpressure flapper in the outlet side of the turbo and make sure it isn't stuck.pull the doghouse out of the van and take the heatshield off the engine.you will see a rod that comes out of the turbo pedastal and hooks onto the flapper linkage(jesus clip).take the clip off and unhook the rod and see if you can turn the linkage if you cant then the flapper is stuck.you will need to free it up its hard to do on a truck without removing the turbo but on a van i think its possible.
just something to check and it won't cost you a dime just a little time and some wd-40 or pb blaster