I have installed the passive kit from Strutmasters' on my 94 'STS. I got the kit for the front and the rear. I kinda believe the kit from Arnott would have given a better ride(they make kits that still use air in the back), but when I found that I could buy the whole front/rear kit from strutmasters for less than $420 shipped to my door, it was easy to make my decision. I purchaced this car to keep miles off my 04' Monte SS...NOT to go broke getting the car to ride like it came off the assembly line. If that's what I wanted, I woulda baught the cheapest OE replacements I coulda found.
The strutmaster rear shocks are little baby's compared to the factory, electronic-controlled air struts. The shaft on the stockers is almost 3/4 of an inch thick. Strutmasters rear shocks(they are a shock with a spring grafted onto them to create what they call a coil-over) have a puny shaft (maybe 3/8), similar to a regular gas shock for a regular rear drive car. The shaft is covered with a piece of hose to take up the space inside the rear upper strut mount...The fronts seem to be direct replacements with the exception of not having the electronic plug in the back side.The kit looks to be designed for a cheep way out of air ride troubles. The kit doesn't have anything fancy, but will do the job. No more Cadillac ride, though. I will get used to it...
As far as rattles, squeeks, and noises. When a car has enough time on it that the suspension needs replaced, there are bound to be other items that will need replaced as well. Replacing the bad parts will make the parts that are half-way-there stick out like a sore thumb. I had noises after the passive conversion. I found most of them. One was the stearing rack. New inner tie rods($15 a side at A-Z), and an all wheel alignment, as well as 4 new tires, cured that "funny" feeling from the steering. The next noise came along with a "shimmy" at low speeds, over small square-edged bumps. Front stabilizer links were the culprit. One end mounts directly to the strut, other to the control arm. I checked them when the struts were out, seemed O.K., but didn't pay too much attention to the lower part of the link(control arm end). With the car on the ground and someone moving the car up/down while I checked made the problem obvious. A-Z could get them for $43 a side, but decided to take them off first. Thats when I realized it wasn't bad, just loose!!...Another issue solved. After that I had a few other noises I figured out(2 golf balls in the glove box, loose speakers in the trunk, etc.), but its pretty decent now. I would in no way compare it to a factory ride, though...
As for the resistors, Strutmasters says you don't need them if the small electronic shocks that attach to each corner of the cars suspension(I can't think of what they're called.) are in good condition. Also the STS has a 2 wire plug on each shock/strut. The kit's instruction were a little sketchy about were to put the resistor, and my electronic mini shock thingy's were in good shape, so I first spliced them into the plugs that were pulled from the factory struts/shocks. The "Service ride control" light still came on, so I pulled the plugs for the mini eletronic shock do-flochy's, and put the resistors in that harness... Same issue. The passive kit doesn't have any electronics to plug in, so the harness has to be deleted from the car. I still have the ride control warning light on, though. It hasn't bothered me enough to dig into it any deeper, yet. I can turn it off once it comes on, but it comes on again every 15 miles or so...
I would spend the extra dough for the Arnott kit if I had to do it over again, and money wasn't an issue. The Arnott kits are only a few hundred more than the Strutmaster kits, and still use the air-ride.
I am happy with the ride of the Strutmaster kit because of the cost. Everyone has different reasons for making thier choice, BUT, if it is for comfortability, spend the extra dough. You wont be happy with Strutmasters...