What are the possible negative effects of running the Tokico D-spec shocks on an '04 Coupe 6MT with stock springs? Obviously lower and stiffer springs would help, but am I introducing new problems by keeping the stock springs? Thanks!

 

I don't see any. You could probably adjust them to oem stiffness if you like. You may want to watch which version. Is the D-spec designed for lowered Gs? If so, you may run into hyper extending them?

 

I doubt they're designed specifically for lowered G's. In fact, the full length DSP-7 shocks should be fine w/ stock _height_ springs. The DSP-9s (made for 350Z) might be too short.