All Toyota engines and almost all Ford engines - including the 4.6L/5.4L/V-10/7.3L - will show high silicon levels for the first 50,000 miles. These engines use a glob of "Permatex" type sealant to form the oil pan gasket. Small amounts of this material are also used in other places - at the ends of the camshafts for example. If you see high silicon levels in one of these engines, do not assume it's dirt. Look at the levels of wear metals that are used in the intake system, such as nickel/chrome/aluminum/iron. Also look to see if bearing wear, ie lead is elevated. The silicon levels from my 2.4L Tacoma engine dropped from 50 ppm every 10k miles to 10 ppm every 10k miles. However, it took 50,000 miles for these levels to stabilize.