mixing racing fuel

[Talitmon@aol.com]

Has anyone mixed high octane racing fuel along with their
regular fill-up at the station for the VR6?  Like BP's 110 octane,
or Union76's etc., etc.  
Notice any performance differences? Have any bad immediate
or long term effects on catalyc converter or other engine 
components?  
I have done this on my other car without any negative effects, 
at least none that I knew about. (5.0 liter tuned port IROC)

Thanks for any input.........
Talat 
97 GLX
Blk/Blk