it is to a point..bigger than factory is usually good..but if you just put a 600x300x100 hybrid $200 core with 3" in and outs, on your stock 180SX expect a bit of lag! also, most of the off the shelf cores you by at autobarn and things like that, are usually bar and plate..these give the best flow through the core, but at the cost of efficentcy..a tube and fin however is more efficient at cooling..i have a custom PWR core only a little 450x250x75 custom end tanks etc etc..the core itself is capable of flowing 400hp at 1 bar (quoted from PWR) i can't remember the pressure drop, but is was equivelant to a bar and plate core of a bigger size..i'd rather have an intercooler that cools the air better than one that flows a little more CFM..having said that..the differences are pretty negligable..