All right so quick backstory, 2011 G 37 all-wheel-drive coupe. 130 K, spent its entire life out west. No on the East Coast. I've had it for about four months, and have driven it in rain without issue.
I put an oil pressure gauge in it just to make sure that Galley gaskets were OK.
Good oil pressure when hot, around 20 to 25 pounds.
Fixed the sunroof leak issue, a long time ago. Because I felt what on the floor, and just did the bypass to the HVAC box. No more wet floor.

About four weeks ago, I got rear ended, and the car after it got hit at revved up, installed out, I'm assuming that was probably some fuel cut off thing. I had a code for a VSS, P1721. But I think it had been in there for a while. No check engine light, driving home in the rain the other day, 2500 RPMs and I'm not going any faster.
I didn't notice after I got off the freeway, that it was starting to clear itself out. The only other modification I've done to this car is Z1 cold air intakes.
Took it through a car wash twice this weekend, and twice with the same result. I would have to manually shift up or down, and then it would get normal again once it seemingly "dried out"
I am at a loss here, and with no check engine lights, and no codes, I don't know where to begin, please help

 

The ECM and BCM are under the dash on the passenger side. Because they are essentially computers/PCBs, they are unpredictable when "moist" since everything other than pure water is a conductor because of dissolved salts and minerals which act as charge carriers.

In addition to the sunroof drain, water can also enter the car through the firewall gromet and via the cowl (plastic piece under the wipers).

Is the cabin filter damp?

 

you know, I thought about that, I haven't checked the cabin filter. But it is kind of strange how that thing just hangs out there underneath that cow. Being that I disconnected the sunroof drain because it was plugged, do you think it could be getting in from there as well? I don't have any moisture on the floor. Not anymore anyway when I first bought the car, that's what I noticed. I had a damp smell, when it rained. And that's when I was like oh must be a sunroof drain. So I fixed that. But I have driven it in the rain since, and not had a problem. This is something that's new. The only thing that changed as far as the cow goes, as I did run a wire for the oil pressure sending unit through the firewall, but that was on the driver side. And I RTV it off.

 

If the windshield cowl is leaking then water will be pooling in the blower box and the fresh air filter will be saturated. Typically, in this scenario, your electrics (BCM, ECU, etc.) should remain dry. Now, if water is leaking past the firewall grommet then your electrics can be affected as they are in the direct path of water as it leaks down to the floor. Either way, with enough rain, water will be evident on the floor.

You said your car was "rear ended." Was it a minor bump or was there actual damage? Any chance some the rear wiring was damaged? I ask as VSS error codes, like the P1721, can be tied to wheel speed sensor issues, BCM/ UMAC amp, or, worse, TCM issues. If the "hit" was severe enough" it is possible some wiring was damaged or perhaps a connector at one of the wheel speed sensor(s) was knocked loose.

Given your issue presents "when wet" leads me to suspect a wiring issue likely at the rear wheel speed sensor(s). I can not guarantee that is the cause, though... just thinking out loud.

 

It seems it was the CAI! I'm going to go through a caress today to make sure.