On a 540 with 871, will i benefit much with some porting on the Dart Pro I 325cc models?

That question is best given to JimV on this site. PM him and see what he suggests.

Jim V's cell: 616-889-0928

Absolutely, A big misconception is the relation between boost and airflow. Boost is pressure, or measuring the restriction. The more restriction the higher the boost. More airflow will lower the boost with about the same cylinder fill. With chamber porting, the stock Pro ones exhaust ports can be improved 15% or more depending on the header size. The intakes about 10% depending on the valve size. To say how much power increase depends on cam size and other factors