plugs, wires, oil, stabilizer and all that other cr@p don't make more than 0.5 hp on such cars,.. except that the power is only accessable higher up in the rev range.
please avoid fondling with a ca which is designed to haul you and your shopping from the market to the house. these are "shopping trolleys" and not performance cars.
if you are serious about power then you should either go for an engine swap or leave the car alone.