I think what this thread has largely focused on, is where do you (realistically) draw the line - and while yes - the best answer is to always to phone and ask, just to be safe - we all know that’s it’s ridiculous to phone about some things which - if you were being incredibly petty - could be classed as a modification.
I’ll hopefully be re-painting my grill before the spring rally - it’ll be black, as it was when new, but likely not the exact shade (unless somebody can tell me the paint code for the standard grill on a 2003 Sport?) - should I phone Admiral and let them know I’m painting my black grill black? It won’t be original after all.
What about if I take it off, and then decide I’m not capable of such a complex task, so put it back on, but in the mean time lost one of the original screws, so have to replace it with one which is not 100% identical - have I modified the fitting?
The clip that holds my breather pipe in place broke (or rather, somebody (who in all honesty was not me) broke it) a few months back - it’s now held together with super glue (and doing its job perfectly well) - but you could argue that since it’s not 100% as it was when it left the factory, so it’s been modified.
If I replace my juddering clutch with the (genuine Mazda) modified non-juddering part…
See my point? - You can take the word ‘modification’ to an absolute extreme - one which we all know insurance companies won’t care about, so somewhere between a turbo charger - and a slightly different screw - is the point that you 1) Should phone your insurer, just to be safe. & 2) Need to phone your insurer, because you could never plead ignorance (“I didn’t think a jet engine on the back would make a difference…”).
If you can just take 30 seconds and phone up, and ask a question that would be fine - but insurers (especially non-specialists) don’t work that way.
For a start, for some reason they’ve always got to look up your policy, regardless of what you ask them, which means you’ve got to tell them your life story so they can ‘verify your identity’ for ‘your own protection’.
Then you need to explain to them as clearly as you can what you want - they then go to their supervisor, and ask them. Inevitably they come back to you with a question (typically covered in what you already told them).
Then they go back to their supervisor again (who is clearly a good example of the Peter Principal) who still doesn’t grasp it, but obviously felt forced in to giving some bizarre response. So, you have to clarify the situation with the guy on the phone (who for some reason won’t let you speak to their supervisor directly), who has another bash at explaining it, and this time comes back with a response that sounds along the lines of what you expected, so you assume they’ve grasped it. (When in reality they’re probably wondering why on earth you’re telling them you burnt what your grilled bacon so now it’s black).
Even if you have the list of “Modifications you do/don’t need to declare”, if you bought your car used, how do you know what was standard fit? - Especially on a car like an mx5 which has precisely 50 million special editions.
My car has a low-fuel warning light. I’ve always assumed it was made after Mazda started fitting them - but maybe it was a mod by a previous owner.
Ask a dealer, you say? - That’ll be the same dealer that when I asked for a set of wiper blades for my 2003 mx5, asked me if it was “for the front?”
But that’s a whole other can of worms (and should be discussed in another thread)