I've pretty much made up my mind on ordering a '13 S4 and picking it up in Germany next summer. I don't have garage space or time to keep the MSP, but I've got a collection of parts laying around now and I can't decide what to do with them.
The MSII is working out of the car with the JimStim, but I haven't grown the balls to cut up my unopened patch harness to actually put it in the car.
I have a beautiful powder coated crinkle finish red valve cover that I spent the better part of the day polishing the logos on along with the requisite Mazdaspeed oil cap. I haven't put it on because I bought a new VCG and figured if I have the VC off, I should probably do the timing belt even though I am only at 76k miles. So I might as well do all the belts, idlers, tensioner spring, and water pump. Since I was doing all that I figured I'd replace the pulleys with aluminum ones while I was at it. I could never find the water pump pulley so I've got 2 of 3 on my workbench.
I also had a hot pipe powder-coated to match the VC. I had bought the hot pipe just as an experiment to move the WGA vacuum source in front of the throttle plate, but it arrived in such poor shape I had to clean it up. Moving the WGA source to the hot pipe will essentially lower my boost, so I bought an MBC in order to bring it back up, but I won't put an MBC on the car without some sort of EMS to monitor it. I had already sold my FIC and started on the MS, so I decided to wait until I had my MS working to start anything, which brings me back to the patch harness.
I also have an MS flywheel which I had planned to put on if and when my stock clutch ever let go (back to the unsprung mass kick), but it's still as strong as ever. Hurray for rev matching.
There is nothing really wrong with the car that wasn't wrong from the factory. I am getting a little tired of the 800rpm vibrations from the MM inserts, and I've debated taking them out, but anyone who buys this car is probably going to put them right back in, so I probably won't bother. Also, my neighbor with the engine hoist moved and I've never felt comfortable supporting an engine by its oil pan. Always seemed like a good way to get it to start leaking.
The problem with all this stuff, is that it's worth a whole lot more off the car than on it. Mods don't increase resale and most of the time hurt it. It's well over a grand in parts sold separately but on the car, they really aren't worth anything. A new timing belt and water pump might help the listing, and the bright red VC might look attractive to the right buyer, but I wouldn't even try to sell a car that is running off an aftermarket PCM, especially a homebrew one like the MS.
I know what the smart thing to do is, but if all we ever made was smart decisions life would be very boring.