mk1 1335kg - mk2 1400kg
well the 18" wheels are defintely heavier, but as for the rest of the 65kgs…
the mk2 has loads of extra gizmos, cruise control, xenons, auto headwipers etc, different subframe, different body panels, different engine covers, different interior, larger side pods etc…
Ive never heard anyone mention a specific part that makes up a large part of the difference so it must just be the combination.
a few people have stripped a mk1 of 100kgs+, but not heard of a stripped mk2 yet.