Most early 4-valve engines were not good at low-to-middle speed torque, simply because the larger intake area resulted in bad slower speed air flow. At low speed, the slow air flow in the intake manifold led to imperfect mixing of fuel and air, hence knocking and reduced power and torque. Therefore 4-valve engines were regarded as strong at top end but weak at the bottom end, until the technology of the variable intake manifold became popular recently. The aforementioned Chevrolet Cosworth Vega performed particularly weakly at low speed.
In response to this, Toyota introduced T-VIS (Toyota Variable Intake System) in the mid-80s. T-VIS accelerated low speed air flow to the manifold. The theory was quite simple: the intake manifold for each cylinder was split into two separate sub-manifolds which joined together near the intake valves. A butterfly valve was added at one of the sub-manifolds. At below 4,650 rpm the butterfly valve would be closed so by raising the velocity of air in the manifold. As a result, better mixing could be obtained at the manifold (excluding direct-injection engines, fuel injection always takes place in the manifold).
However, for later mainstream saloon engines, Toyota dropped this idea and adopted a small-diameter intake manifold / port design. Many other car makers also went the same way, sacrificing a bit top end power to improve low speed flexibility. Today, the introduction of variable intake manifold can solve this problem.