All insurers want to know of any modifications made to your vehicle that are not OEM and take it away from standard, OEM spec - that includes bumpers, any other armour, and any performance mods. Whether or not it makes a difference to your premium is up to the insurer. The last time I renewed, one company (which said it welcomed modified vehicles), thought my mods were too much and wouldn't cover it. As you can see, my mods are not exactly extensive or radical. My own insurer couldn't see that they made any difference, and gave me a good quote, so I stuck with them.
Failure to inform an insurer of mods is usually a ground for them to withdraw cover in the event of a claim. That's the case over here - knowing insurance companies (and I've acted for a few over the years), I'd be fairly surprised if that wasn't the case where you are.