[MTXA]

I've found a little more information since this post. I think I'm going to try hunting down a used 0-3 or 0-4wg gauge. One experiment I'm interested in doing is measuring the pressure at the rear of my car and seeing if using a nozzle to direct the air that passes under my car to reduce the lower pressure at my hatch. This is different than using a diffuser in that I'm not looking to shape the lower pressure zone but rather actually break the suction. It's my understanding that pressurizing air has less impact on efficiency than the drag created in the wake. I've already added a front lower tray and want to verify that the pressure under my hood isn't increasing as a result which could cause poor flow through the heat exchangers.