2.5" ID is rare for a hose size. I've seen people use a combination of PVC hoses and the joints as their intake pipe. They wrap the thing with alu sticker and superlon to keep the heat from melting the thing. It's quite ingenious if you ask me.
Drex used discarded pipes from other cars that he worked on to make a intake pipe that goes from his manifold to the area where the u-snorkel is supposed to be and down into his bumper where the open pod is. Very clean install and no worries about water suction. Not much intake noise either but all the benefits of a long runner and a open pod!