I like option 3 for my 1990 240sx. My plan is to cut a 3” hole in the passenger side bumper using the existing angle facing downward under the direction signal area and finish it off with a black plastic 3” OD desk grommet $12.00.
Standard Plastic Grommets - Rockler Woodworking Tools
I have also purchased a 3” OD electric RV automatic waste valve so I can close the pipe when it rains. The electric valve two flanges and remote switch under $90.00 shipped. Call 8777878833 and explain the purpose they will configure it for you needs. I selected two male 3” on both sides. Female is also available at
www.Drainmaster.com. I purchased a 3” Home Depot metal twistable angle pipe that connects the front plastic grommet to the valve. I have not figured what kind of tubing I am going to use to bring the air from the electric valve into a 3” hole, which will come, through the battery tray. I also have to make a short tube to connect directly to the intake manifold and swing right to connect to the MAF / K&N. What to do with the battery? I prefer to install it on the driver’s side. I just have to figure how to move the fuse box out of the way. This is a much shorter and colder air route then on top of the radiator and across the engine compartment. My current K&N filter with the stock air intake gets very hot. It was a wasted move with my hot headers for summertime use. I think I am going to make a metal header heat shield like the stock unit to deflect the heat.
This is all taking a back seat because of poor idle and gas mileage.