So after a long wait I finally got the plenum and 74mm t/body installed. Did it after work last night and finished tonight, it took about 3hrs in all. In the end I went for a K&N filter rather than the 987 air box due to time constraints, also looking how much space there isn't it looks a pig of a job!
Hard to get many thoughts on the way home as it was wet and dark so giving it full beans on country road didn't seem to sensible. I have a trip over the Yorkshire moors to Whitby this week so we'll see how it goes.