Mace 25mm spacer install issue

I had to do the plugs on my wife's LY7 CTS, so I decided to go ahead and try the 25mm Mace spacers that I had read about. The install went fine except for one of the replacement bolts in the kit being too short (taken care of by Mace right away - great company to deal with). The problem is that the back of the plenum is so close to this bracket that sticks off of the firewall that it taps against it when the engine is running. Drives my wife crazy. Has anyone else had this problem with the thick spacers?