I know the Governor Mod has been talked to death on here but I don't think we really have any one single thread which defines it and gives good graphic representations of what is done.
First off I should say that unless you are very comfortable with your mechanical skill you might want to reconsider doing this. This especially applies if you have no back up transportation, it's Sunday night, and you have to be at work at 8 AM. Things just go wrong sometimes no matter how well you prepare yourself. Depending on how much you shim the springs it may also be possible for you to over-rev and damage your engine. You are your own warranty.
How does it work? Well, essentially this spring pack opposes the force generated by the flyweights as RPM increases. By shimming these springs we are increasing the spring rate and therefore increasing the opposition to the influence of the force generated by the flyweights. The overall result is that the governor is not able to effectively reduce fueling at such a low RPM and the overall range of operation is increased allowing the engine to rev higher and make more power.
Some of these pictures are my own and some are gathered from other places on this board as I haven't taken pictures of everything there is to take pictures of.
First I should start with a picture of the pump top.
This is an NA pump off of an 84 Rabbit so it doesn't have the LDA. The bolts are still in the same places though.
The circles on the left show the relative area of the bolt locations. The throttle lever assembly must be removed to access at least one of these bolts. Notice there are hash marks around the shaft and a notch in the top of the throttle shaft. Those must be aligned back where they were otherwise the engine could race or not accelerate. This is an '88 Jetta TD pump top:
You may also find it necessary to retract the fuel screw to get the pump top off. At the very least it will make reinstallation easier.
Once you have removed the throttle linkage, pump top bolts, and retracted the fuel screw you should be ready to pop the top off. Sometimes it may take a couple taps of the hammer to break it loose. When pulling it off don't force it and as you pull, push on the throttle shaft as to force it back through the bushing and out of the pump lid.
Now that the top is removed the governor assembly will be visible. The assembly should look more or less like this:
Notice that this one is shimmed and has one spring removed. The spring assembly would normally look something like this next one with the main, intermediate, and idle springs.
Before it was shimmed the car would fall on it's face by about 4500 RPM. Now it continues to make power up to around 6000 RPM where I suspect the engine airflow becomes the limiting factor.
When reassembling the pump it would be a good idea to replace the seal on the pump top as well as the o-ring on the throttle shaft.
I'll try and update this again as I find more pictures but I thought that'd be a good start.