Hi Jorge,
A lot of programs that I've configured have a step at the bottom of the program that asks "Sent to CRM". This filter includes only the scores that we want to send.
Lauren makes a really good point. If the feeders to your CRM program catch all leads, then you will send D4's regardless of the logic in the lead scoring program. You could put a step at the top that asks "is lead a D4?" and have it exit if it is.
The only thing I'd be careful of is if you're excluding them from the CRM program, you may be excluding them from being updated at all. If they fill out a form, you may never see that information in your CRM. Depending on how you're creating campaign members, that information may be affected as well.
Happy to answer any more questions - just @ me!