I've recently fixed this with a combination of the following parts:

Monoball rear LCA bushings, solid thrust arm bushings, rear toe arms with spherical inner bushings followed up with an alignment to 0.5 degrees total toe in, equal amounts each side in the rear.

 

Check ur rear toe arms and alignment.
How r ur tires?

 

Tyres are still like new, but we installed some Eibach springs months ago.
It's not that I assume or it would have done this before.
Today I'll have a look underneath to make sure everything's still tight.

So you guys dont think it was the traction kicking in then?

It's strange.

 

It's funny...I've never had that feel. Ever. I did solid thrust arm bushings, monoballs on the LCA,brand new tires, and an alignment, and that exact same feel was really noticeable today just cruising at 80mph. :-/ my alignment is -1.6 camber and .24 toe.

 

Wouldn't that just really **** you off! I checked everything under the car to day and it's all normal. I think the PASM kicked in and stopped me going off the road. I'm sure the technology is what caused this because it's only ever happened once.
When you think about the brutal power these cars have it's makes sense.

 

You may want to read this.

https://www.6speedonline.com/forums/...lp-needed.html

 

If you got the wobble like i had under hard acceleration at high speeds I honestly think its suspension/toe arm related.
Check the bolts for the toe and camber if you havent but research when it happened to me pointed in that direction. Since then I've had the springs lowered to H&R, been on different tires and had the alignment done. During the alignment we found my toe-arm was bent including the bolts.
If it keeps happening over and over I would lean towards suspension issue vs psm traction issue but good luck finding out and update us if you fix it.

 

The issue is he either needs an alignment (because the rear toe is out), or he's getting too much flex in the suspension bushings.

I would start with monoball cartridges for the rear to links.

Later, Steve

 

Hard to imagine partial boost being enough to cause the PSM to kick in.

You replaced the springs. Did you have the car properly aligned afterwards?

Before you even leave your driveway though check the tire air pressure, all 4. Once under very hard braking from extreme when I hit the brakes the car veered quite sharply. It wasn't a tank slapper moment but it was closer to this than I ever want to be again.

Not knowing what was wrong but knowing this was not normal I pulled in to a gas station and found a rear tire down around 6psi.

Filled up the tire and headed to a nearby dealer -- in Fresno, CA -- and on the lift the tech found some nails or screws in the tire. Tires were quite worn so worn the tech and another tire store refused to fix the tire.

Might add before I left home the tech who gave the car a road worthiness inspection mentioned the rear tires were worn and suggested I have them replaced before heading out. I had planned on getting 2K more miles from the tires then having them replaced once I arrived at my destination. Obviously the tires didn't make it the 2K miles.

Had to back track halfway up the state of CA by way of Livermore, then Walnut Creek, and then the next day eventually to the Sacramento dealer who had a full set of tires available.

 

My first experience with this sensation was doing a third gear pull while logging. While the rear end was wobbling back and forth at 100 MPH I thought, "that's scary. I wonder if it's PSM.". So I turned off PSM and did another third gear pull. Equally as scary. I concluded PSM was unlikely the culprit.

As I stated before, I have since replaced those parts in the rear suspension along with monoball shock mounts and am yet to experience that sensation.

 

It got worse.