So what are all the changes the stock engines have seen since "99" model Gen IIIs came out?
Mainly I'd like to hear any major mechanical electronic or fuel system upgrades dome to either increase power or fix some issue.
It would be nice to have a running list of things like this.

I know from 99-00 ther was an injector upgrade but not sure sizes and reasons.

 

I think the 99-00 Injectors were 19# and the 01-up are 24# could be wrong.. computer upgrade from 00-01, 05's got Efans.. All I could think of for now..

 

Big change was 03 to present was the removal of the EGR system..

 

I thought there was a change with block in 03 that affected the oil flow, where 2002 and older blocks had only 2 holes to allow passage of oil, and the newer block had the whole area bored out.

 

99-00 6.0 had iron block and heads, and the longer crank
01 and up 6.0 has aluminum heads (317 casting) and shorter crank (LQ4 or LQ9)

99 had a different camshaft from the 4.8-5.3's to the 6.0...I think they all used the 6.0 cam after that (except the LQ9)

 

the throttle is changes from a cable to wire in 2003. can u changed the intake from the wire to cable and everything work like it is suppose too.

 

The 03-up have no return on the fuel rails and the regulator and filter are in the tank.
Also no PCV.

 

Lets hear what has upped the horsepower ratings from 99-06.
I know the injector size went up like I stated in the 1st post, I think the intake tube was redesigned slightly.
So what changes took the power rating from the 99's 5.3l from 275hp to the latest 305hp?
And how about those 4.8ls and 6.0ls. I know they built more 5.3s than the other engines but I never really looked into their original HP rating then VS now.

 

My 03' has a return line and regulator on the rail.

 

My '02 does not have an EGR system. I think this change was made in '02 not '03. My '01 tahoe does have the EGR system