On an ST200 a shielded cone filter (like a Pipercross Viper) gives greater gains than a panel filter or an open cone. We tested one on the rollers and, more importantly on the road using an air temp sensor. The 200s engine bay is very cramped and heat soak is an issue with a cone filter.

While power gains can be had the cost to gain just a few bhp makes it a little pointless, if it was mine I'd save my cash so I could afford to put petrol in!!