John, because I have some experience with the 'Not/Illustrious combination (you of all folks knowing why), I will probably mention some things that you have already done but that others might find useful. I would first suspect the azimuth as Tom has mentioned. Check the arm pod of the Hyperspace first to ensure that it is plumb and level with the platter plinth. Next, make sure that the collet ring is seated "plumb" such that the arm pillar is perpendicular to the platter. After these are successfully accomplished, check the azimuth (with a small spirit level on top of the headshell is possible). The Illustrious CAN be adjusted for azimuth by CAREFULLY loosening the hex nut located behind the headshell, CAREFULLY rotating the headshell, and the CAREFULLY re-tightening the nut. I am told that the re-tightening is most crucial so as not to collapse the arm tube.
The wire cradle for the anti-skate "bob" (according to OL) should be at approximately the angle as shown on the template provided. HOWEVER, there are many who believe that this cradle is best set to be perpendicular to the arm when the cartridge is positioned at the outer edge of a record. Too, the cradle is held with a tiny hex screw and it can get out of vertical - loosen the hex nut and make sure that the wire is fully seated in its "hole".
Heres to hoping that you get back to your original sound. Oh, one last thing. Make sure that you tighten the two grub screws on the collar JUST tight enough to keep the arm from falling. Otherwise, if one is tightened more than the other it can throw of the pillar and put it out of perpendicularity! :-)