One thing to keep in mind with CT...they produce several different mods. CT_raid being one of them and the smallest. I run the entire CT Suite of add ons (well, download the entire suite, but run most), and that does add some overhead. The basic CT_Raid that is available is small, and shouldn't bog the system down too much (I say shouldn't, but I obviously do not know your system like you do).
I just wanted to point out that if you downloaded the full CT suite in the past, I can definitely see that slowing down an older computer, but just the CT Raid part of it shouldn't add much overhead (once again not saying it won't slow down your computer, just want to reiterate that there are different CT add-ons).
I run into this with the Onyxia runs I lead, but fortunately for that it is not as critical, but I have to remember to call out deep breaths over TS for those that don't have CT Raid.