If you never declare it and hit someone it depends on the company but i very much doubt they will cover it. It won't cost you too much extra............unless you have the car chipped. I declared my and it cost me 150
when i was looking for quotes a few years back .. just the SS exhaust put the cost through the roof but now with everything declared .. even stuff like exterior trim mods need declaring sometimes brentacre basically let you do what the hell u want to your car as long as you stay within the same power bracket out of interest who is your quote with Darryn? (mine is 450 3PF&T, 3 ncb, 23yr old)
well my insurance is 1000 ha ha and thats 3rd party. wrote off my fiesta in jan 2005. im 20 with no NCB although this year will be 21 years NCB well technically 2 as one was as a named driver. hopefully see 600 fully comp this year as ill be 21. Gunna declare everything, not worth the hassel. I know someone had a mk1 1.8 16v on log book it was only a 1.3 needless to say his insurance company didnt pay out. he lost his licence and now drives a 0.7 matiz and insurance s over 1500 ha ha ha hes only 18.
When i rung up to find out about mods, lowering didnt add anything to the policy, and alloys ( 17inch ) would mean i would have to pay excess on my policy if i had a claim! So your better of declaring them!