I weighed my SR20 with the quads and it came in at 96kg.
I weighed my A15 without exhaust manifold of intake manifold and it was 69kgs
I weighed the webers and manifold and it was 8kgs so all up 77kgs...
now I reckon 20kgs difference wasnt too bad...especially for the extra power.

I think the weight in the SR is in the plenum...quite heavy and the iron exhaust manifold, very heavy flywheel and power steering pump this would bump the weight up to the 135kgs quoted