2018 Skoda Octavia engine performance ok but i get excessive white caper which blanks the road out this is when you floor the throttle it does clear after 3 /4 blasts

If not losing coolant , probably just condensation . But if as bad as you say and in doubt carry out a block test which will tell if head gasket leak .

I'm a retired mechanic ,I'm sure it shouldn't do it but I don't know why ( help)

Its only dun 18k there is no water
Loss ,I think it is a build up of water in the exhaust &when you floor it it blasts it through

If only doing short journeys and engine not really reaching working temp you could get water build up .

Thanks for all your info & advice
I think the fault lies in the design
& shape of the two tail pipes were they come out of the rear box they dip down then sweep up ,as an ex
MOT tester I have seen small holes drilled in silencer boxes,
maybe that's what I should do.