While we're on Suncorp-Metway....
This is a rough paraphrasing of the conversation I had with them. Driving history, age, rating and mods carry points. Based on your age and rating you are given a certain amount of points. A bad driving history, speeding fines, accidents and the like consume some of your points. Different mods have different point values. Once your total points exceeds their predefined limit for your situation you are an unacceptable risk. Wheels and bodykits are included as mods. I couldn't even have mags on the car and not have them insured. Likewise with a stereo.
Based on my history, even though I am 25 and a rating 1, I am allowed 2 mods. Each mod adds to the excess, the first mod adds $600, the second takes it up to $800. However, the premium was relatively cheap at $1400 (on an R33). From memory, I had a quote from Just Car Insurance quite a few months ago at $1700.
I have a theory (cue x-files music) that others may be able to confirm or disprove. If you ring an insurance place with a car that is already modded rather than insuring a car and then modding it, you have more chance of getting insurance. It seems they are more than willing to get you through the door but once you are in, the door is locked. I could be wrong but that's how it seems to me.