2001 Chevy express runs great in park bogs down in gear?

i just changed out the spider, plugs and changed the oil after my injectors went out on me and now the van doesn’t run well in gear.

when in parked or neutral it runs just fine but as soon as it goes in gear it starts knocking and struggling.

any ideas?

 

I would have the cats checked out.

 

check your fuel pressure

 

Is the check engine light on? If so what are the codes?