New to the forum...I have a 97 Subaru Legacy 2.5GT that has had all plugs, wires and the coil pack replaced in January.  Just 2 weeks ago, the CEL came on, with a cylinder 4 misfire; took it in to my normal shop, no problem found.  Just a couple days later, CEL on with cylinder 3 and 4 misfire.  Again, took to my normal shop, no problem found.  Moved to Las Vegas, CEL on during trip.  Took it to another shop, same error codes (cylinder 3 and 4 misfire), but no obvious problem.  The car runs great, it is definitely not misfiring.  Any ideas on what this could be?  BTW, my gas mileage is better than it's been in a long time!  Clueless!  Please help   
  
MORE INFO!  The codes were consistent of P0304 and P0303.  Once I *STOPPED* using my car charger for my phone, the errors stopped being thrown.  Any ideas on this one???