As long as you don't choke off (reduce the 3" diameter) there's nothing wrong with that setup as far as airflow. The static loss from any extra 90's should be negated by the increase in the size of the pipe. Besides I think it looks much better behind the cab.

If you're worried about it loosing airflow you can buy a Magnehelic gauge for about $30 at Grainger's and take a static reading on your current setup. The best place would be at the Carb/TB airbox. Just make sure you take your readings at a fixed RPM (like 2,500) and not at idle. Make your changes with the new pipe and then take another reading at the same location. If the static pressure increases then you've restricted the pipe.