hi 172Gal, before starting on the slippery road to mods (i.e financial oblivion) what are you looking for: increase in performance, noise, show etc. Have an honest think and the answers/advice we can give will be very different!
on a bang per buck basis IKs are a mostly a waste of money, but they sound good. If you really want performance and cant be bothered with noise/looks, save up your cash. There will soon be some vewy vewy juicy power modifications available for mk2 172s!
ps. if you ignore this and stick on the viper irrespective (thats what my wife would do when being advised to the contrary, so Im assuming theres a good chance
) you may be better off updating the ECU map (they simply increase fueling to compensate for extra air). If you intend to stop there, go superchip at power engineering, or hill power. cheapest. If however you make further mods, a superchip will not follow you through your new mods and itll be money wasted. A unichip then becomes a better bet (what I have). If you go further to Throttle Bodies, you can scrap even your Unichip as you will need to replace it with a proper ECU e.g Motec, etc...
Decisions, decisions...