I'm with AAMI (comprehensive). Since March 09 they have increased the amount of modifications to a vehicle, to infinite (according to the help-dudes on the phone) which is another reason why I started modding this car... First 4 mods + Stereo to my MCV36R Camry didn't cost me any extra; despite increasing the agreed value from 12k to 15k. The mods were CAI, Exhaust Modifications + Extractors + Non-standard alloy wheels. My premium for Jun09-Jun10 was ~$1100 @ Rating 3. When I got it lowered, I had to pay $126 upfront for the remainder of the insurance period. I recently called up to see how much extra it would cost for coverage for a supercharger and was quoted @ $57 for the remaining period, this is with an increase agreed value to $17k. I haven't bothered with other insurers since AAMI has been good for me.