In case any of you have never used racing seats, I had MOMO's in my turbo mk4 jetta and when I took them out later I didn't have the same feel/confidence to take corners as fast even though the suspension mods remained( coil overs, sways, bushings, mounts). I don't even mean at ten tenths, just out on the road carving corners I noticed myself taking them about 10 mph slower because of perceived roll and traction limits.
So changing seats actually made a real driving difference to me that I thought wasn't associated with them at all. Hope that helps some people pull the trigger. I know I'm a big guy and still slide around in my ss seat.