p0300, p0301, p0306 codes

i have a 2003 3.4l tacoma 4x4 double cab.
twice in the past 2 weeks the engine has run rough within minutes of starting (in cold weather, 30-40 degrees) and then returns to smooth within about 5 min. the codes i'm getting are 300 301 and 306. the guy at the auto store says it's probably the coils on 1 and 6. i find it difficult to believe that these two coils would simultaneously crap out, but return to normal function once the engine is warm. i figure that replacing the plugs is a good first place to start, but i assume that multiple misfirings would likely be traced back to a common source somewhere upstream (ie, MAF, fuel filter, etc). any assistance would be greatly appreciated.

 

300- random misfires detected
301- cyl. 1 misfire detected
306- cyl. 6 misfire detected
If it smooths out when warm sounds like a intake starting to leak. I would have a smoke test done when its dead cold.