ak_uk and wallisj on here both have have HP IKs fitted to their 172 Mk2s and got good results on the rolling road. Both needed the ECU modding by HP to compensate for the engine running lean with the IK at high revs. The HP IK kit is based on an ITG foam cone filter with some heat shield around 2/3rd of the filter and a cold air feed on the exposed section.
Personally, I reckon the Viper is a neater solution, although more expensive. roamer got excellent results with a SuperChip...
Also, it is pretty evident that the air filter setup as std on the 172 is very restrictive, so any of the above options should yield performance gains!