That depends on the details of your database design and what you are trying to do.
The look up function is the "looked up values" field option set on certain fields to copy data from related records from "last year"?
You want to use Import Records to import data and you don't want this to take place?
If your answer to both questions is yes, there's an option that pops up during record import titled "Perform auto-enter options while importing". Disable that option and the look ups will not occur. This is an "all or nothing" option so there may be other auto-enter options that you do want to occur during import. If so, you'll need to add a follow on script that loops through the newly imported records and performs the scripted equivalent of each such auto-enter option.