Cornering
 

I've noticed on sticky PSS tires when I corner vigorously the back end feels like it's wobbling/hopping around and basically feeling unsettled. This is usually at speeds where the stock tires will start to squeal (35mph+).

What kind of suspension upgrades would I need to improve this? Stiffer springs/coils? Swaybars? Stiffer bushing?

Change your driving habits, alignment, play with tire pressures, and report back. Once you figured out how the car responds to these different inputs and you have maximized the capability of those, then you'll have a better idea of what you're looking for for your application. :thumbup:

get better suspension, you wont regret it
I just bolted on a ohlins kit for my e46 and am pretty impressed, bet the one for 86 is as nice

+1 to this. Was told to never throw parts at problems such as this, but to instead embrace it and change the way you drive the car. Just throwing parts at this situation could only compound the problem IMO, and does not fight bad habits. Not saying this is a bad habit, but merely a change in dynamics meaning your driving style must reflect it.

That being said, I am no pro driver or pro mechanic or pro anything. Just tossing input.

So it could be driver technique? Smoother inputs?

I've noticed if I do the same thing with stock tires, the car remains smooth but with stickier tires it becomes unsettled. I was thinking it was due to the stickier tires (and maybe higher speeds) emphasising the movements in the suspension.

Absolutely could be driver technique. With stickier tires you are actually probably turning in harder then with the stock tires. Just try to turn in smoother, if the road allows it start slightly wider.

With "stickier" tires per say, the time it "wipes out" is much shorter than with less sticky tires. The limit before adhesion is lost is much higher, but the amount of time to cross the limit to completely sliding is much less.

You may also want to look at all the other factors as stated. Also, unsettling may mean you're also traveling at a higher pace than before. Keep in mind, the speeds can be different as well.

Driver skill ranks above all. The driver's ability to take advantage of the tire compound is what driving is all about. You can't rely on equipment to always let you go fast.

100% why I faceplam whenever people change out sways as their first suspension mod. Especially ridiculous track setups thinking they can still DD it nicely or to "combat bodyroll"

The stock car is much better than many suspension kits out on the market. Driver mod is very important but also learning about what the capabilities of the factory vehicle is also equally important. Toyota/Subaru didn't throw millions of dollars just to be outdone by a company that tossed $500 suspension at the car and said it's better than factory.

Did you observe this behavior with all of the electronic controls enabled? If so, you should try the same maneuver with the traction control and VSC shut off. These systems can apply the rear brakes one at a time which could result in the conditions you describe. Better yet, since the console button never totally disables this system, do the pedal dance and then test the car again.

How many miles (or kilometers) are on the car? If quite a few, it would be worth checking the rear shock absorbers. My are shot after only 40,000 miles.

I avoid driving on public roads without the nannies on and I don't see the traction light come on when carrying out the cornering. There's one turn that I always experience this so I'll probably try it with VSC sport to see if it makes any difference.

Car's only done 10,000 miles (weekend toy) so I don't think it's the shocks.

I'll save up the money and work on driver mods. It makes sense that with stickier tires I'm pushing it way harder than when it was on stock, and in the process being too aggressive with my inputs. I'll do more experimenting with the stock and PSS tires and see how it goes.