Rear toe, acceleration and thrust, any gurus?

[dfv2]

My static toe is/was pretty damn zeroed out. I run a GC M setup out back including M arms, koni yellows and eibach springs. EC-7's with 275's in back.

Before I get my summer alignment (street use, no tracking but like it aggressive for no real reason) I'm looking for any feedback you guys have:

1) Is WOT toe-out because of the squat and geo, or is this a bushing slop thing (both)?

2) If so, do you guys prefer some extra static toe-in to compensate for stability when going WOT or loading up the rear tires?

EDIT/UPDATE:

Resolved with proper alignment. Driver side rear gained some toe-out when reinstalling M arms for summer, and thrust load plus toe-out = crazy town out back.

[fe1rx]

That is really interesting, but I have no comparable video to compare it to. Unloaded bump steer is virtually zero at the rear. Certainly too little to see with the little squat generated. That has to be bushing deflection due to thrust load, presumably in one of the links, but possibly in your subframe if they are worn asymmetrically.
It does look like way too much toe change to be normal to me.

[dfv2]

I was shocked when I saw it too, maybe the toe opened up over the winter months a bit, and it's so far out the thrust exacerbates things. I need to inspect the bushings back there too, I'm making around 460-480 rwtq so it's always twisting about.

[dcaron9999]

With all this Torque you are producing, did you/are you considering an aftermarket rear toe arm kit?

Im on stock suspension, slight tune, Quaife 3.46 final drive LSD, and probably get some deflection in the rear as well, although never documented or filmed. I dont put down as much power as you do, but did change my Diff ratio from 3.08 to 3.46, and converted the chunk to a Quaife LSD. There is definitely stronger torque at the wheels since I did these changes ...

The guys at my local speed shop did an outstanding and meticulous job, even simulating the suspension load and unload to optimize front and rear toe. They also equalized the pressure in the tire to what I typically run at the track. I never experienced such attention to details during an alignment. I cannot wait to try this out on the track next week.

This is the alignment Im starting the 2014 season with on my dual duty 135i, tailored for the track (pardon the French):