As far as I know, the Cusco bar will almost surely not fit the IS300 properly. While the photo shows a Cusco bar on a 2JZ-GTE equipped Supra, the throttle body is placed differently (here its on the side, while on the IS it's placed on top, lowering the amount of clearance under the hood) and of course, the Cusco bar is designed to fit with a 2L inline 4 as opposed to a 3L straight six. I considered importing the Cusco bar, but the amount of work it would take to make if fit the IS would make it quite expensive, but then again if there were a lot of people willing to put some money down on it, we could try importing it and see exactly how much would have to be done to make it fit right.