I drive an 04 WRX. I have a friend that has an 04 STI. He just replaced his sway bars and gave me his old ones. My first question is would the stock STI sway bars fit on my car and my second question is would it be worth it?
the front will, the rear will not. As far as I know they are the same front bars though... sorry. Hold out for his struts and springs! And wheels!
Not worth it at all. front is only 1mm larger, the rear is, depending on if you have the 20mm or 17mm...is either 0mm or 3mm larger and requires modification to the rear endlink configuration. Again, NOT worth it.
I put an 06 sti's rear sway on my 03 wagon. I had to get the brackets from an 04+ so the rear swaybars will fit. They were about 3 mm bigger in the rear, and the front was the same as my stock. I noticed a difference, although my endlinks pop, I am still using the stock endlinks as well and hope to be upgrading soon. Best thing to do is climb under your car and hold the bars up to each other, or take a wrench to check the sizing.