My 98 Impreza L has a tendancy to oversteer and fishtail around turns a little bit. It's most noticable when I hit a bump in the middle of the turn, and is more pronounced in turns to the left than the right. Start a turn, hit a bump, and then feel the rear end swing around a little bit.

 

It also seems to exhibit more bounce on the right rear when I hit a bump, like that tire is bouncing like a basketball after a bump on the highway.

 

I'm thinking that I've got a bad strut or two. Could there be a different problem?

I'd be looking at my suspension bushings.

How do you tell if they're bad? Get the weight off the rear wheels and wang on the lateral and trailing links and see if they wiggle?

[...]It also seems to exhibit more bounce on the right rear when I hit a bump, like that tire is bouncing like a basketball after a bump on the highway.

 

I'm thinking that I've got a bad strut or two. Could there be a different problem?

It could also be be tire-related. Are the two rear tires the same (type and wear), and are they evenly inflated? What pressure are you using? Anything possibly bent or otherwise out of alignment?

I looked quickly and didn't see anything bent, but I don't really know what I'm looking at yet.

 

I did notice that the rear sway bar can be wiggled just by grabbing it. It seems awfully thin compared to the front sway bar.

 

The tires are the same type and show the same amount of wear. I inflated them all the same, 44 PSI. It's not quite as bad as it was before when the tires were all down around 35 PSI.

I looked quickly and didn't see anything bent, but I don't really know what I'm looking at yet.

 

I did notice that the rear sway bar can be wiggled just by grabbing it. It seems awfully thin compared to the front sway bar.

 

The tires are the same type and show the same amount of wear. I inflated them all the same, 44 PSI. It's not quite as bad as it was before when the tires were all down around 35 PSI.

Unless you have actual damage, it's the rear struts.

 

Yes, rear sway bars are much thinner. There are conflicting opinions on the efficacy of a rear sway bar. Some say a thicker bar give you more precise feel of what the suspension does in a corner. Others say a thicker bar just lifts the inside rear tire off the pavement sooner, and actually makes the car slower in the corners. Some Subarus have so much horsepower it's often a tossup whether confidence or equipment is more important.