Below 10,000? Yes...air gets thinner as altitude increases, of course, but it also gets thinner as temperature increases.
Try this on your E6B: in the "For True Airspeed and Density Altitude" window, line up the +15 "Air Temperature" tick mark with the 0 "Pressure Altitude" mark and read the Density Altitude....you get 0 Density altitude. Now, move the wheel so that the +35 "Air Temperature" tick mark is aligned with the 0 pressure altitude mark and read Density Altitude: Just over 2,000 feet. Same airport elevation, higher temperature, higher Density Altitude. The airplane will perform as if it's at 2,000 feet.
Now, set that +35C temperature over 5,000 feet pressure altitude on your E6B and look at the Density Altitude: 8,000 feet.
The turbocharger isn't there for speed, but to compensate for density altitude by increasing the pressure of the air going into the cylinders, which makes the engine produce the same power as it would at lower altitudes. The turbocharged engine will be less affected by thinner air, and therefore will deliver more power on a hot day, giving you better takeoff performance, too.
Edit: corrected the E6B example
