If you aren't reusing the pipe, which you shouldn't be, you can cut it. However, depending on the bolt, you may be able to just slide the fitting apart (assuming the rest of the bolts on that flange came off okay).
If that doesn't work, go to the tried and true method. Grab a drill and a good bit, and drill the old bolt out of the hole
Zetec....is that like Vtec or something???
Zetec Crew #103/ATX Faction #27 (retired)