This makes no sense to me

I doubt a straight tube will work. In all I've seen the tube has been bent a little to clear accessories. I'm sure when their made their all straight and different accessories probably make a difference on how and where it's bent so the factory leaves them straight so you bend them to fit your application. You just have to be careful when bending it not to kink it. I bent mine to clear stuff successfully and have done several others as well.

It might make it easier by using a tubing bender to put some bend in it before you install it so you shouldn't have to remove any accessories to get it to drive straight in. Using a tubing bender should also help you not to kink it. Also grease the bottom up to make it slide in easier like 6pakdemon said.