R33 hicas is not mechanical, it's electrical - your getting the hicas is in limp mode, lets stiffen the steering wheel crap... If you have stock ecu try doing the HICAS diagnostics test - there should be a thread about it on this forums!
Ps: my car does it to, i got used to it, so over trying to fix it (I can't run diagnostics because I have a microtech ecu)