This has been discussed before:
http://www.zr1netregistry.com/forum/...hlight=porting
Will you feel the difference? everday driving = no, winding up to redline = yes.
90-92 models have more to gain from porting. Other breathing mods will complement a port job.
Personally I think every ZR-1 should have a ported intake, headers and free flowing exhaust, these mods really bring the LT-5 to life.