Hi Diego,
I had a read through your build and love the work you have done. For me and my build I decided that the S3 had to stay in the realm of the "family car' whilst at the same time seeing just how far one could take it before losing the full compliance and driveability. I own a very highly modified 2.0 16v Turbo 4WD Corrado and this is where I too have given in to the Dark Side
With regard to the IE inlet manifold performance improve my post map, it is hard to say. The reason being that I fitted this as part of a package before the map, so I can't say exactly what improvement it made on paper. However I can say that it certainly made an improvement with response. My reasons for using this part were too ditch the plastic inlet which I have little time for ( I don't like plastic inlets they cause way too much trouble in my experience), to delete thoroughly the runner flap system, to incorporate a manifold with direct to port WMI injector feature, and to improve induction characteristics for my upgrade package. I feel the IE inlet has achieved all that I wanted.
I read that you have interest in a WMI system. I looked at them all and have chosen Aquamist for my car. It is a fantastic piece of kit that works exceptionally well on the car. The engineering and thought that had gone into the product is beyond any question. Richard, at Aquamist is an extremely well informed and capable engineer and he developed for my car an all new injector to fit the IE inlet manifold perfectly. It is straight forward to install for a guy of your clear ability and set up of the system really isn't complicated. The reward however for fitting Aquamist is well worth investing the little bit extra for what I consider to be the best WMI product on the market. We at JMR Ltd are now Aquamist stockist and installers. As a total aside, WMI on big diesels is a real crowd pleaser. We recently fitted HFS4-V3 system to an A6 3.0 TDI along with hybrid turbo and exhaust mods. Result 240 BHP and 419 lbft of torque.
. Whilst waiting for my IE parts I revisited my checks on the stock OEM rear trailing arm bushes. Using a pry bar I was able to get an astonishing amount of movement out of these bushes. Despite these being brand new parts I was not at all convinced that they were up to the job and given that all else had been changed it was really looking like it had to be the trailing arm bushes or another diff warranty claim. So I fitted the powerflex trailing arm front bushes and today I road tested them. BINGO!! No more knock from the rear under spirited acceleration in 1st and 2nd gears 
