Over the weekend, I got talking to a nice guy on facebook called Garry who had spark plugs like mine. He said that one of his k&n's were on incorrect and that the carb breather holes were being blocked by the filter housing. I went to look at mine and sure enough one of the filter housing was on upside down, therefore blocking the two little carb breather holes. I changed it over o all holes were clear and now the revs come down to their previous point after pressing the gas. They come down, which they did not before.
Now they do come down a bit much slightly before returning to their original point (850 - 900 RPM). For a second while the revs dip, it sounds like it may cut out, but she quickly goes back to the starting point.