We've been talking a lot about it here. It seems that there's no good answer: there'll be as many people who'd claim theie inquiries made all the difference, while there are other who claim that inquiries just make CIS be pissed at you. See my case, I've been sending many inquiries and they maybe did make them look at my case,but I got transferred, which prolongs my case for quite some time.
So I'd say send an inquiry or two, follow the inquiry procedure. Probably it won't make a difference; If you hear from them, it'll be "allow us sufficient time to process your case"