There are a few different solutions

The most exspensive being the JUN GT Surge tnak manifold . That is atleast 2K though .

Hux puts a larger plenum on the stock runners and just ports them out . You still haev the somewhat unever runners . His is around 500 $'s though . Much mroe affordable . I think it also comes with a larger TB not sure on that though .

There are also a few otehr but some stopped being made . Truleo made on as well as LB who makes some nice GT Turbo kits for SW20's

Your best bet is to get on the MR2 boards . http://board.mr2faq.com Go on there an do a search for Intake Manifold . Should being back alot of posts .

Hope that helps