When driving down the road the van will start jerking

Scan for codes and check fuel pressure first with a gauge

Try cleaning the throttle plate on both sides with choke cleanerif it still does it have the injector professionally cleaned with either gm upper engine and ijector cleaner. Do not use the stuff you put in tank tis won't be strong enough. They have to hook up to fuel rail and clean that way.

Multiple misfires are very hard to diagnose, have a pro scan it and freeze frame it to seeif anything is out of whack electrically. A lot of times sensors won't set a code but will read wrong voltage wise so they can try changing that part. One other thing if this has s K&N type filter on it clean it out but don't oil it, clean the maf and see if that helps. It's only with those type of filters not factory ones. You could check for a vacuum leak with choke cleaner as that can cause it as well then or if you have done this tuff do a compression checkon all cylinders. If there is a 20% variance on any of them then check to see why on the offending cylinder/cylindrs. Of cours it cold be ahead/intake gasket leak as well if you are losing coolant.