This is very general post. We can't say why the system is slow when the ENS is there. You have to specify when it's becoming slow like all the time or certain time like when ODS is running. what are the component is there. which process is taking high cpu/memory / I/O.
with all these details we can come on some conclusion. Please post more this so that we can help you on this.
i would add to the clarification requested the ENS version too and whick kind of Policy is used (Low risk, let macfee decide, etc..)
FYI ENS 10.5.2 and since a few days nos 10.5.3 brings many performance improvments.