According to TWG a mod was something that isnt in the manufacturers options book/list. When i asked does this include roof racks, tow bars, car seats, parrot hands free's they couldnt give me a straight answer and said they should be fine. The T&C of these policys is very vague and can be interpreted in a way to invalidate claims so i made sure with car2cover by ringing them as i have £1500 of audio in my car.