I'm not entirely sure what makes the VXT so much heavier but at a guess off the top of my head: the alternator is excessive, heavier flywheel at a guess, iron block, heavier cast crank probably to cope with more torque, heavier rods to cope with more torque, turbo, heavier cast exhaust manifold probably, extra oil+water pipes to turbo.
I know that Nipper is now a very heavy 939 KG with 1/3 tank of fuel (so more like 960 Kg with a full tank). Making the car heavier does negatively affect it's "flingability" for sure, but ultimately on any sort of semi-decent road surface (ie not the wheel bending terrible B-roads near me) the negatives of adding that weight are completely offset by the positives of the extra power and torque.
Edited by Nev, 06 September 2013 - 01:32 AM.