[StingRay]

The info I got was to leave the back one out. Keep the front one to help keep crap from getting in on the front side. Build a dam on the front side of the sensors with silicone but leave an opening at the rear of the dam for the recess to drain. Silicone the grommets in and around the wires. The engine is usually angled to the rear and leaving the back out and the opening in the silicone dam lets any water that gets in drain out the back while the dam directs it around the grommet. A LOT of stuff can get past the intake runners from the sides. They are only sealed at the ports and you'd be amazed at the crap that washes down into the valley cover area under the intake.