Thanks. I hadn't considered air density.
It didn't seem to have this condition previously in colder temps, however. My main concern is malfunction/damage to the supercharger and/or related components and I didn't want to ignore any early warning signs. Other than the boost indications, it seems to be running normally. I can hear more of a whine on acceleration since I replaced the stock air filter with a K&N. Other than that, it all looks good.
Any inspection or maintenance tips on this thing?