Here's a thread I found for ya on the 93 octane search in Des Moines. Sounds like WDM and 27th, and across from the WalMart in Altoona?
http://www.desmoinesgasprices.com/Fo...age_no=1&FAV=N
FYI, I've had a fee cars around here (IC) now running 93 available at only ONE known source here with good results. It's only a few cents higher than everything else, but a buck or two more per fill up seems a small price to pay for peace of mind and better performance?