3.5" will not hurt you at all.
My co-worker runs 5" from his turbo to the rear bumper on his truck, and its not a diesel.
That truck is stupid crazy, it will bust the rear tires loose at 55 mph.
He had to turn the boost down to 9 psi just to make it drivable.
19 psi made the truck worthless, un-controllable.
