Complex sentence: It used the same engine as the Moskvitch 403, but fitted with Weber carburettors giving 81 hp, but this was boosted to 92 hp when fitted with the Moskvitch 412 engine.
Split into simpler sentences: It used the same engine as the "Moskvitch 403", but was fitted with Weber carburettors giving 81bhp. This was boosted to 92bhp when the car was fitted with the Moskvitch 412 engine.