It may be that you have had one claim albeit nearly 5 years ago and the mods on the ST are bumping the price up? How much would it be without the claim and the mods - just for comparison purposes. Having previous experience in a hot hatch also helps. I was told that owning a Cayenne turbo did not give me exeprience to drive a Subaru as there a powerful car

Although I agree that Insurance companies are hard work to deal with and it makes you wonder how some things differ so much.
I was been nosey last week and chucked a few reg numbers into comparison sites and was quoted £480 for an ST. Last year the insurance on my bog standard powered WRX was £750 and this year it was under £500 - Im not knocking

but wtf?
You need to shop the market - like what your doing but it doesn't help when companies don't get back to you. I think the biggest rip off is the legal cover and other bolt ons ....