Power lag after carwash

[Overdrive]

maj75 is pretty much on the same track I was thinking of. It's possible that maybe this underspray is making something unhappy, but unless you never let the car see rain I figure the same thing would happen when driving in rain.

Are you being careful not to spray directly at and into the air intake on the driver's side when you're hosing off the car? Whether you've de-snorkeled the car or not, it's still possible to put a lot of water into the intake box if you're spraying right at it.

Do you leave the car running when you wash it at this place?

[stephen wilson]

Even driving rain won't spray high pressure water Directly up.

[Steve Tinker]

I'm betting that the OP has at least one coil pack with a cracked surface...
Having a high pressure under chassis water wash or driving at high speed in heavy rain will cause a faulty coil pack(s) to "short" via the water to the chassis instead of firing the plug(s).

[Lobo1186]

I had a similar problem once with a 6cyl mustang. What had happened was the water had gotten into the distributor cap and messed with one of the cylinder's current causing it to miss-fire only under heavy acceleration. It just seemed to be down on power, when in fact it was having no or little ignition.

Now, it could be possible that since we have coilpacks on the boxster that one was fouled by the water or somehow water broke the seal is is messing with a single plug. If it is having a hard time getting a good spark it could miss fire or have a poor ignition.

just my thoughts.