woofage, see my post in this thread. - bottom line is a fair hike. Some companies wouldn't quote for a modified car - mine is with Norwich Union via the Institute of Advanced Motorists insurance brokers.
A few of us are using Frizzell's, who don't charge extra for any modifications - the only thing you can't do is change engine capacity (CC). There have been a couple of quite recent threads on insurance in this or the general forum.
Around here, the 192 HP kit has been replaced with a 185 HP org. SAAB kit for the 9-5 and 170 HP for the 9-3! This upgrade is off. SAAB with full warrenty and TüV approved! Concerning the actual HP output its up to you to declear the difference with your incurance company!