Tire Pressure Monitoring System Error?

[Kerry]

I have a base 2007 with TPMS and 17" wheels. Last summer the system and my tire gauge gave the exact same readings. I put winter wheels and tires on last fall (with Tire Rack TPMS) and the readings were a little below my guage. I did switch the computer to correct 17" winter "tyres". I now have the original summer tires back on and switched back to 17" summer tyres on the computer. The PTMS reads a very consistent 3 pounds under the "actual" pressure. I am defing actual as the same reading I get from my old guage, a new guage, and a gas station guage.
Any thoughts or fixes? I'm still under warranty but not sure if it might be operator error, and not the boxster.
Thanks

[knurly]

Assuming you followed the procedures outlined in the owners manual for resetting the TPC system, and let it recalibrate, I would say it is time for a warranty trip to the dealer.

I usually have to reset mine about once a year, after getting errant TPC warnings for low pressure. Once reset everything is fine.

[Kerry]

I went to the dealer (Porsche Exchange in Highland Park, IL) and after reading the TPMS they put more air in the tires. The service manager said that the TPMS units are always spot on accurate and to trust it over my multiple guages.

Does this make sense to you all?

What I of course should have then done was simply to check the pressure in one of their new cars with my guage, and then see what the TPMS read, but I didn't think of that at the time.

I don't want to fixate on it, but should I check with another local dealer, or just enjoy the ride?