Yeah sounds to me also like you have a bad pair of shocks.. How low is your car sitting? I'm running Tokico's with stock springs and this never happens, however my rear does sit lower than my fronts and when I had 5 people in the car I still didn't manage to bottom out. Not sure about the drop with the Tanabe springs though.
Sound like you got some bad shocks. I had some very unpleasant experiences with the Tokico shocks. I was running them with the H&R Lowering springs and in 4-5 months, I had to completely replace them twice. This was completely unacceptable to me since my car is not used too often since I drive trucks across the country for a living. For the most part, my car was only used every other weekend. After 2 complete sets (8 shocks), I finally changed over to KYB-GR2 and have never been happier. They are a little more stiffer than the Tokico's and they take out that mushy ride that you may be experiencing. Like I said, you probably got a bad set of shocks. Replace, if you were happy with them, but I would suggest going with another brand all together.
Anybody running Tanabe Springs on UCF20?
Please post picture, wanna see how low it will be
My local speed shop advised against Tanabe - said quality wasn't as good as H&R or Eibach. I got a 1" drop from the springs and about another inch with the Bilstein HD on the lowest perch (almost 2" like the Tanabe). If you go with Tanabe please post how you like them.