Can you say what your Orchestration is doing? I'm wondering what you're putting through it. It may be that you can break this process up into component processes, but this is coming from standard development best practices.
Can you find a way to break the .tif files out and process them separately? You can receive the .tar file, break it out and send the "parts" to another port. I guess it depends on what data you need from the original file(s) and at what time.
Another simple suggestion is to see how you would implement it "without" BizTalk and verify if either way makes more sense, as well as making it easier to see how to implement a solution with BizTalk.