As many would know, I have the W557 package on the 2017 HSV. No way would it pass emissions in any State nor would a few other things in South Australia. In SA, you cannot make changes to the ECU, camshaft, cats and intake manifold. Period. No engineer Cert can overcome those things. So my car is unroadworthy according to the transport regulation in this State. My insurance company is happy with the mods but like all of them they have a get out clause about roadworthy.
But having said all that, I have searched Google using many terms and cannot find anything about a company rejecting a claim based on Walkinshaw mods and a very minute amount with regard to other mods (such as undersize brakes). With thousands of Walk's, Harrops etc on the road you would think the net would have something. So while I am sure Insurance companies could refuse if push came to shove but they don't seem to do that. Naturally, certain things would make them look harder (single vehicle accident, DUI, driving a car than you licence does not allow) but I am willing to take the risk until somebody points me to a link where an Insurance company refuse a claim on a Walkinshaw package having been specifically (as in W557) notified about the mod. My car is brand new, looks stock with the only external mods being the exhaust and I would find it hard for the exhaust to cause a claim.