From this link you can disable the 130MPH speed limiter by just removing a plug on the engine ECU
http://www.intendedacceleration.com/tip_9.html
This is easily reversible and does not require the ECU to be reprogrammed
Tech Tip No. 9
Ned Ritchie
Originally published in the quattro quarterly
Copyright 1997
Audi S4 130 MPH Speed Limiter
The Audi S4 and S6 have a 130 mph speed limiter. It pulls strongly up to 130 mph and then it just cuts out gracefully and limits your speed. In Europe these cars go much faster. How can I get around that 130 mph limit here in North America?
When Audi first introduced the S4 car in late 1991 as the 1992 S4 it came with an all season tire package with 130 mph rated tires. As a car manufacturer how would you make the car so that someone doesn't end up suing you after driving the car over 150 mph blowing out the tires and killing someone.
It's simple. You hire a little guy to sit inside the car to watch the speedometer and when the speed reads 130 he pulls the plug. In effect this is just what Audi did, but they did it electronically.
Some Audi engine turners would like you to believe that you have to buy their performance computer to get rid of this speed limiter; however, here is the truth of the matter.
WARNING!
The following instructions will remove the S4 speed limiter.
Proceed only if legal in your area.
You must use Z rated tires on this car after this modification.
You are also morally obligated to tell new owners about this requirement or put the speed limiter back before you sell it.
You don't want a lawsuit any more than Audi.
INSTRUCTIONS TO REMOVE THE 130 MPH SPEED LIMITER
1. Remove the plastic trim center piece in the front passenger's door sill. It is removed by prying it upward.
2. Remove at least the two screws closest to the front of the sill to loosen the sill.
3. With a small flat bladed screw driver pop out the circular plastic cover at the lower portion of the kick panel trim piece in the front passenger's foot well.
4. Remove the screw that is under this little circular cover.
5. Gently lift up the front of the door sill that you loosened up in the first 2 steps and remove the kick panel trim piece. (Note the trim piece is also attached by clips running up the side of the door jam)
6. Remove the floor mat and carefully cut the foam backing behind the cut in the carpet where the floor meets the tunnel in the front passengers footwell. I've seen some carpets that were not carefully cut first and when the mechanic pulled back the floor part of the carpet it ripped and tore away from the tunnel area. This is intended to be cut O.K.?
7. Pull back the carpet and remove the two large Phillips headed screws from the plastic cover where the passenger's feet usually rest.
8. Lift up the plastic upper cover about one half an inch and pull it downward parallel to the angled portion of the floor. It is held in place by plastic tabs at each side of the top. If you pull it out too far you bind the tabs and it is difficult to slide the upper cover downward.
9. Now remove the plastic lower cover. The upper cover acted like a shingle over the lower portion.
10. Remove the four Phillips screws that hold the computer (the square shaped metal box) to the floor and carefully lift out the computer. You may lift out the relay rack that is above the computer for easier access to the computer and to make it easier to remove it. Notice how everything is placed. You'll have to put it all back.
11. Under the computer you will now see a piece of wiring with a receptacle on the end with a plug stuck into it. The whole thing is held in place by a plastic clip. Carefully pull up this plug and receptacle. This is the engine coding connector. Pull out the plug and put the receptacle back under the plastic clip. Lay the plug on the floor of the plastic compartment so that you can find it when you want to plug back in the speed limiter. (CAUTION! Do not unplug the computer unless the ignition has been off for a minimum of 30 seconds. Special circuits are still doing things after you turn off the engine!)
12. Replace the computer by reinstalling the 4 screws, and the relay rack if you removed it.
13. Put everything back the way it was by reversing the above steps. The hardest part will be the replacement of the plastic upper cover over the computer. The two tabs have to go into the slots on the top first
NOTE:
The results of following of these instructions can be read by an Audi mechanic using the following Scan Tools:
VAG 1551 Scan Tool
VAG 1552 Scan Tool
Intended Acceleration's
Laptop Scan Tool Program
With these tools the code can be read in about 15 seconds.
The coding of the Engine Control Module is 4 which is valid for both the U.S. and Canada.
These instructions changed Coding 4 to Coding 1.
Coding 1 is valid for European countries and does not contain a speed limit.
For the technically minded:
Terminal 38 of the computer is grounded by the coding plug described above to obtain coding 4. This is accomplished by bridging terminal 1 to 4 of the coding plug