98 S70 T5 - Trouble codes P0455 and P0108

[TBoone]

I've pulled the following two codes from my 98 S70 T5 and need help:

P0455 Evaporative Control System - Large Leak detected - I replaced the fuel cap about 5 weeks ago, but the code appeared again within a week. I'm told that it could be the Evap Cannister---how do I check? If not that, are there hoses or sensors that can be checked?

P0108 MP0108 AP/BARO Circuit High Input - This has appeared since the original diagnosis of the other code. Is there an obvious repair for this?