With many thanks to Roger-Cheshire i now have a K&N air filter installed. More fiddly to fit than i imagined due to a hidden air-box lid screw - double joined fingers would help!
Result? Its difficult to determine exactly what improvement it gives - not that much i suspect, however the already keen to rev Sigma seems even more responsive - i suspect the gains are greater when revs are high.
Having followed Rogers advice by also fitting the lebrands side exit exhaust at the same time i must agree 100% that for less than £100 these small, easily reversed, additions add greatly to the car.
Andy, I'm so pleased that you feel as I did. It was amazing how much more responsive it felt. If you haven't done already, fill up with 98 octane and thrash it to within an inch of its life! That also made a difference and was a pay as you go improvement!
