Installed the SRI and torsion bar today. What a difference!
I'm not sure how much I can feel the SRI's improvements in the high end, although admittedly I probably need to let the ECU program itself before I really know what I'll get. There's a definite improvement between 4k and 6k or so on the highway, which is promising for track work. The noise is the real upgrade in my mind, though, the car finally sounds as sporty as it feels!
The torsion bar makes a gigantic, immediately noticeable difference. I just hit a twisty short road next to my house, which isn't a true test, but even at 5/10ths in a single lane I could feel a little bit of oversteer starting to show its head, and through the really sharp stuff the rear is super solid and the car rotates like no FWD I've ever driven. It's just point and shoot. Heck of an upgrade for $99.
Video coming soon, the parts didn't come until 7:30 so it was dark by the time we were done. I shot a before video and used a decent separate audio recorder for the sound so once it's all edited together it should be a pretty good reference for what to expect with the SRI.