Ive been searching but i cant seem to find what i am lookin for..

ok here is the problem:

I have a 94 gsr with i/h/e but lately it has been runnin crappy. it does not revv smothly and when i rev to like 6000 or higher and let off the gas it sounds really sick, almost like its a V6, i cant really explain it. Also sometimes it will not go any faster unless i downshift...it sputters and jerks the car. The check engine light comes on every once and a while but goes off if i shut the car of and then re-start it. I checked the Cel and it #43, which means it has something to do with the fuel system. I just changed my plugs and wires, and fuel filter and its still doing the same thing. Can it have something to do with the vacuum lines? I can find any info at all about vacuum lines so can someone please tell me more about them

any input would be greatly appreciated

-chris