If you have any large vacuum leaks it won't idle at all. I'm assuming it runs just won't idle or doesn't run stable at all? Bosch invented this way of controlling engine emissions using O2 Sensors for the mix ratios. Make real sure the EGR valve is not stuck open, if it is it's like having a 1/2in pipe hole in the intake. Naturally aspirated engines can't handle a stuck EGR. I've slipped thin aluminum under the port then gently tightened the mounting bolts enough to black off enough air leak to prove a faulty EGR.