I'm with Desert Captain.... The V10 should not need higher octane, except to buy time until the proper repairs are made. Besides a contaminated MAF, a intake or vacuum leak can also cause it.
I've been running 89 for towing (22,000 combined) because I had intermittent pinging from a vacuum and/or EGR leak. Because of my high miles, I just had everything gone over at once, and I'm fairly confident I'll be able to tow with 87 octane again. At least until the temps rise. Above ~90F I still need 89 octane, because the program I run is fairly aggressive with the timing advance.