No piston slap is never normal, except as you found in the contrary from Lexus.
Poor metallurgy and long term wear is one reason; however, relaxed production line tolerance is another (given other new ES on the lot suffered the same).
I thought these days every manufacturer matches pistons to cylinder bores to achieve the necessary tolerance. Well maybe not Toyota (which makes Lexus line).
Piston slaps: "essentially, the piston moves sideways and "slaps" or "knocks" hard against the cylinder bore and causes damage to the engine pistons and cylinders, excessive smoke emissions, excessive oil consumption, carbon buildup on piston heads, decreased mileage, and a loud and obnoxious "slapping" or "knocking" noise, all of which diminishes vehicle resale value in the trade."
Maybe someone else besides me doesn't think that "piston slap" in the ES350
> is "Normal".
> Graybeard
>
>
> >
formatting link
>> > Lexus Division>
> > Lexus passenger cars reported April sales of 13,766 units, a
> > decrease of 22.1 percent from April 2007. Passenger-car sales were led
> > by the ES entry luxury sedan with April sales of 5,439 units. The IS
> > entry luxury sport sedan reported combined sales of 4,550 units. The
> > LS flagship luxury sedan reported combined sales of 1,992 units. Sales
> > of the GS luxury sport sedan reported combined April sales of 1,568 > > units. >
> > Lexus Division light trucks reported April sales totaling 9,584
> > units, down 8.6 percent from the year-ago month. The all-new LX 570
> > enjoyed sales of 799 units, an increase of 207.3 percent. The RX
> > luxury utility vehicle posted combined April sales of 7,160 units. The
> > RX 400h hybrid luxury utility vehicle reported sales of 1,624 units
> > for the month, up eight percent over the year ago month.