studder with boost & evap control code

i have an 07 s6 with 45,000 mi. i am getting the studder when the boost kicks in and im not sure why and where to begin to try and solve it. and today i got a cel with the evap control system error??? any ideas what might cause this, gas cap was tight plus its been a few days since i got gas so i know its not the cap... no mods the only this ive done so far is change the stock ait filter to a k&n

their is a service bulletin on the evap control system.
"SERVICE BULLETIN:SB-01-023-10 NHTSA ITEM NUMBER:10034005

MFG Bulletin Date: 04/16/2010

Component: FUEL SYSTEM, GASOLINE:STORAGE:TANK ASSEMBLY:FILLER PIPE AND CAP

Bulletin Summary: MAZDA: DETERMINING EVAPORATIVE SYSTEM LEAK LOCATION FOR DTCS P0441, P0442, P0455, P0455. SOME VEHICLES MAY HAVE A MIL ILLUMINATION WITH DTCS STORED IN MEMORY. *PE

Date added to datbase: 10/08/2010"


do you know what CEL # it was?

my friend that checked it thinks it was 1417 but he didnt remember

probably need to spark plugs or them at least re-gapped to .028