Thought I'd share an update.
I replaced the IK with the standard version over Christmas, and run it for a few days to see if it was just a placebo effect upon my intial findings, and as I was going to be travelling hundreds of miles, it has more than enough time to readjust. I found as well as being silent in comparison and allowing my to hear my exhaust again, I found it didn't really want to get moving initially and using the only real upside, which was a little better at pulling from really low down when using high gear and super low revs.
So I changed back, as I still had more journeys to do, so allowed room for readjustment again. I still believe this mod has improved the mid, upper and low down ranges, however when going to real extremes and pulling from barely tick over the standard unit suits my car better. Now I realise all cars are different, but for me on my car, this mod is a welcome upgrade over my standard setup. Plus the noise is nice, loud and grunty. :smile: