Toyota Repair: engine noise at startup, piston slap, mobil 1 synthetic

Question
Hiya terry im the proud owner of a 2004 tacoma 3.4 double cab pickup.The truck has just 6700 miles and has begun to make a bearing noise at cold startup.It is summer here in N.Y so its not a cold weather startup just the first startup of the day.Ive been using mobil 1 synthetic since day 1 and am very dissapointed by this noise.Should i take it the dealer for inspection of could this be piston slap.And if it is piston slap is it normal 4 these motors to do this at such a low mileage?  

Answer
Gee guy, this puppys under warranty I woulden do anything but take it in.  The synthetic is not recommended untill 5k. I rebuilt a old slant 225, 30 over every thing and yes I stared it off with the same oil bad ideal went 3 weeks rings never wanted to seat smoked not bad but enought I thought I broke one but before I tore it a part I asked George, the man that bored it and he said save the oil and run reg mobil in it for 5 k then go back to the syn this worked, right after I changed it it stoped smoking.