first make sure the fuel filter is new, or unblocked and there is no holes in the fuel lines drawing in air, the 8v has a problem with the throttle body gumming up, take the intake pipe off and have a look at the butterfly for gumming. use a brake cleaner spray to clean if off (best take the throttle body off due to the cleaner being very flamable) they must be set up on a computer to get the best results.
hope this helps
andy