Thanks, I was thinking along the same lines. This shop I had install my Koni yellows did an alignment after the install and the car was pulling to the right. Today I took it in and they said it was probably because I added the spacers (they think that threw off the rear align.). But, they are wrong!
At a guess, I don't think so. All of the suspension arms are attached to the subframe, and you move the whole subframe, so none of the angles between the various arms and links should change.

This is intended as a follow-on to Daryl's install thread. His how-to is fantastic, very detailed, so I'm not going to talk about that much. Instead, I wanted to give my impressions of the Peak Performance urethane bushings.

Here they are in their little box. Chinese food anyone?

http://www.sr20forum.com/gallery/data/522/medium/P10100332.JPG

Lined up for inspection:

http://www.sr20forum.com/gallery/data/522/medium/P10100352.JPG

As you can see, the bottom spacers are pretty much the same as the aluminum ones, but the top spacers surround the bushing fully, rather than having a slot for installation ease. They do have a slit that enables you to wangle them around the stud between the subframe and the unibody.

Here's my only install note: heat the top spacers with a heat gun. It'll make them flexible, and if you stretch the slit section apart it'll stay open longer. I had a hell of a time with them before I thought of this.

Installed (rear set):

http://www.sr20forum.com/gallery/data/522/medium/P1010037.JPG

Driving impressions:

These were sold to me as being 99% as stiff as the metal ones, but having far less noise and vibration transmitted to the cabin. I was expecting a "rubbery" urethane like ES bushings, but these are harder, more "plastic-like" for lack of a better description. More rigid, I guess. The install took slightly less than an hour, including two breaks to shoot my valve cover with more coats of paint.

The back end does feel quite a bit tighter; the ride stayed the same, i.e. did not deteriorate at all as far as I can tell. The car does seem a bit noisier especially under engine braking, but I don't find it annoying or objectionable at all. I'm considering a bit of Dynamat or similar in the trunk/back seat area, to keep the wife's complaints to a minimum though.

Overall I'm very pleased with the results. I'm taking a 1/2 hour highway drive later so we'll see how it acts on noisy droning concrete.

Thanks for the addition^^^ I just got back from Deployment