Delbourt

Thank you for that clarity. That at least answers one question when it comes to insurance quotations.

Now I just have to think about why there is a low level backfire when lifting off to change gear or on the overrun (unless that is normal for a TF135).
Revs at this point are most unlikely to be much above 4000 and probably lower. In due course I will have to pay more attention as to when that backfire takes place i.e. what is taking place at the time and what the rpm is.