If the skin feels different (like what you said about having no feeling in the area, it's raised, etc) it sounds like special scar tissue and I'm not sure that it ever really goes away. Is it sort of waxy? My friend had a deep cut on her face from a car accident and what healed over was a waxy, raised scar tissue...and I'm not sure there's much that can be done about it short of plastic surgery
I was in the same accident and was burned very badly across my chest by the seatbelt and I have that sort of "weird" scar skin too, it's a little raised and in an odd pattern (probably the pattern of the seatbelt fabric!). I don't think it'll ever fully go away. What's odd is that my scar does the same as yours, sometimes it goes red and sometimes you can hardly see it at all. I don't know what causes the colour change but I think it might have something to do with body temperature?