Check out this RC Driver article, it goes into header porting in some detail: http://www.rcuniverse.com/magazine/a...article_id=398

The engine used is an HPI 15-FE I believe, so it should be very similar as long as your exhaust is the oblong, rectangle shape, just like in the article. if it is a round header, there would be no material to take off, so you couldn't do it. i don't know what the manifold looks like on the 2.5R, so you'll have to read the article. Hope this helps