never had any problems with mine, they were always insured through flux or hic. if you tell them "I have hydraulic suspension" they will just go "eerrr..." and you can say "it allows me to adjust the ride height from inside the car" and they will say "does it make it go faster..." and you can honestly say "no!" so there should be no effect on your insurance..
my porker has fully adjustable coil overs, arb's, poly bushes, etc., and the insurers weren't bothered. I even changed the brakes to "big red's" and 993 turbo disks and they were cool with that too!.. infact the only thing that effected the insurance was the exhaust, intake, bigger injectors and motec ECU, and even all that lot only added about £25 a year, despite adding about 20% more power..
Its definetly not worth the risk of not declaring IMHO
b
