Back to the spring/sway discussion seems like looking at pics stiffer springs are the answer. I am running lowering springs and 034 FSB full stiff and ST rear bar with -2 front and rear
The 034 bar I believe is one of the softest front sway bars sold for this chassis. It's the same diameter as the GTI stock bar (24mm)... and after having their ball joints I'm somewhat suspect of any measurements they publish (their RCO ball joints advertise 10mm of RC correction... they're 17-18mm taller than stock).
Taking a sway bar from hollow to solid has a practically non-existent effect on overall stiffness (as in less than a pound of force). Most of their added stiffness almost for sure comes from the "A" measurement being different than stock in the chart below.
I've actually taken my own measurements of an H&R 26mm front bar and it specs out as 80 or 120% stiffer than OEM. They sell a 28mm bar which MIGHT be better for autocross purposes.
More info here:
https://www.datadrivenmqb.com/suspension/swaybartheory
And here, while more track-focused, if you have a way to plot G forces might give you some ideas on how to determine if the bar is actually helping or not. Or adjusting between 2 different settings which is a lot more likely to be doable testing for autocross since the course is never the same.
With the 26mm bar on stiff when autocrossing, on 034 lowering springs there's some body roll, but with almost -4 deg of camber (I'm in XA, not STH) I'm not terribly worried about it. I prefer a softer setup overall on track.
I'm currently in the middle of "dynoing" a few different bump stops to try and improve things further. They're way overlooked when it comes to tuning the suspension except for a few little niche automotive circles (Miatas, BMWs).
I've talked to
@mrmatto a bit about it... but I suspect one could probably get some bump stop packers (basically just delrin or plastic split washers) to slip over the shock shaft and play around with the engagement points of the bump stops. Start with something like 15mm in the rear and 10mm up front... will also help move the bias more towards oversteer. The bonus of this is they're easily removable so you can keep your comfort on the road, etc.
Off the topic of suspension setup:
There's some other really fun stuff I've been playing with on the ECU side of things. Basically commanding the throttle body shut (or nearly shut) and keeping the wastegate closed... the car essentially stores boost in the charge pipes so works like a weak form of anti-lag and makes it really responsive, especially in slaloms and coming out of a long sweeper where you're partly on the throttle. It's not enough to stay "spooled" but it takes a noticeable portion of lag/transient response out of the picture. Due to the logic of how the ECU regulates torque, still working through some part throttle driveability issues (sometimes the throttle plate will flutter open and closed), but that's moreso from a daily driving standpoint and hasn't been an issue on course or when driving in anger.
