We designed the GTWORX/BILSTEIN valving profile to work with BOTH the YELLOWS and BLACKS.
YES at one point we offered a hand full of members who were self admittedly, very sensitive to the valving EVEN with BLACKS installed. Keep in mind of the initial batch of 100 sets we sold in mid 2010 only 6 members complained of it being too stiff. Literally the remaining majority checked in with us via PM,email, phone calls, at events etc with super positive feedback. The reality is MOST want this for improved performance and NOT having to get coilover
We have NOT done any revalves in over a year and it is NOT necessary as the existing valving is fine for BOTH blacks and yellows.
What one gets with the Black springs paired to BILSTEINS is a damper that offers a LOT of control AND more comfort than the Yellows which are on the aggressive side.
(disclaimer: all references to BLACKS and YELLOWS is directed to RCE BLACK springs and RCE YELLOW springs). Had a bro roll up on me once " say my man, you said on the internet that Yellows are better than blacks..". I had to explain the whole thing to him. When we were done he wanted a Subaru WRX.