OK, Ed I have to day I think your's stil may not be right.. I went to the TT shop open day on Sat and came accross a o6 plate 310hp Scooby STI Prodrive on the way, (I know the spec the guy got out to ask me what the hell was in mine!) On A5, traffic cleared, I had boost on 3/4 and just left the scooby for dead. At 120 (kmh!) plus, the s3 just shot away and was still pulling hard to 140kmh!
I came up behind an M3 on the autobahn in Germany, last model not brand new on, he was tanking on, but I was just sat behind it flashing him to move! He did so at over 130mph and S3 just sailed past him...
I took a guy who was in at APS out in it one day and threr was a 996 carerra 4 that was hacking along the bypass, we got in behind it, he boted it to go past some cars from about 50mph, I nearly ran in the back of him and was having to feather the throttle behind himt! And it had about 0.2 bar to go on the adjustable boost.
If you are getting wiped by M3s and 911's etc, I really dont think your's is too well. I know you said in previous post the car was laggy and not smooth. If you have a nice torquey 325hp in an S3, I would think an M3 would be no problem in a straight line?
Ed maybe it would be worth having Mike at Jabba remap it for you? Not sure who mapped yours but its a jabba kit, MIke does know what he is doing with the mapping of their kits. A car with our spec nicely mapped should be proper quick. It may well just be with a tweaked map, push the timing a bit midrange (now you have neuspeed thermo and cooler plugs it should take a bit more) that even if you dont get more power, it may be all you need.
You should also consider getting some proper testing gear on it or get to a drag race track and set some times. With your spec you should have mid
13's on the quarter mile at 105- 110mph. If it is not making that, then it is just not right.
It may be worth a trip to jabba to let them have a look and a drive in yours. Mike will know if it is doing what it should do.
It seems a shame to plough more cash into it if you have yet to optomise what you already have......
I also had no money at all when I needed a new clutch and a gearbox rebuild. The S3 out of the box is not very good, and there are cars that are more tunable out of the box, maybe no matter what you spend (depends on how deep your pockets are), the S3 is not going to give you the power you need? Not a criticism, but if you want quick, buy a car that is designed with that in mind in the first place, or get your motor bike license, to get your speed kicks as I did 
