Oh they are right ther,,,,,,, what the hell lol
Looks like in 2004 they removed them for emissions BS Why did you want to adjust them ?
Difference between the GTI's are the engine size and if its fuel injected.
Base is the GTI 717, simple
GTI LE I thing is the 787 engine which is a little more powerfull
RFI is the 787 engine with fuel injection.