Dividing the flow after the collector is not a problem as long as the pipes are not too big (slows the air flow down allowing tumbling).
4-2-1 is ideal but mostly impractical/ expensive. it does add mid range torque but with a big t4 in a light bug torque is not usually a problem.
Mind you even 4-1 have a limited benefit on stock-ish engines.
The 1303 rally engines had a stock looking t1 exhaust (probably an empty silencer) and produced 125hp from 1600cc.