There's a lot of discussion for PSI. Personally I'm using 45 PSI cold on my PS4S, but partially to balance out the edge wear I got on autocross. Also I feel like it may provide more protection for the 20" wheels. You have a P3D Stealth though so no worries for you.
42PSI cold is pretty much fine.
Lengthy aside:
Do note that the PSI indicated in the car by the TPMS is NOT gauge pressure (which is what matters) - it is absolute pressure minus a constant (sea level atmospheric pressure). This means that the TPMS will always read low vs. gauge pressure at elevation, by whatever the atmospheric pressure difference is from sea level pressure. E.g., they will read 2PSI lower than gauge pressure at 4000 feet. Gauge pressure is what matters. If you're coming up from sea level typically your cold gauge pressure is going to increase anyway (assuming temp is the same...which it won't be), so you won't necessarily notice this in the car.
But anyway, no idea where you're at, but relevant for people who live more than a couple thousand feet above sea level and are using TPMS to set their tire pressures. If you live at 5k feet, you do NOT want to use the TPMS to set your pressures without applying a correction - you'll end up overinflating your tires by 2-3PSI.
https://www.tirerack.com/tires/tiretech/techpage.jsp?techid=167
Are you putting these on a second set of wheels? Keep in mind that alternate wheels will also impact efficiency (due to aero design, less so due to weight), in addition to the tire rolling resistance. The factory MXMs plus aeros are very hard to beat. (Someone here is running Pirelli P7+ on 19" and he gets excellent efficiency...but you do need to be aware of impacts on stopping distance.)
I would recommend you use a tire gauge to check wear for the first 2-10k miles, so you can understand how your tires are wearing. Also, some cars have come with excess toe and this will cause premature wear (and somewhat worse efficiency) - good to find that early.
If all goes well after that, you can follow the manual recommendations. But rotation is easy and there's no point in burning through tires due to bad alignment, so keep an eye on it.