what is the difference from a early 99 to late 99

[99strokeit]

i am just wondering what is the difference from the early 99 to late 99 my truck has a build date of march 27 1998 and my friend has a 02 and the only difference i can really see is he has the air heater on the intake and another solenoid on the valve cover can anyone explain what the big difference is

[2ntense]

i think the later 99's also have a bigger turbo.

[alabamafrog]

There is a whole forum subsection devoted to the early 99 Differences between early99 and late99-03 trucks