An offroad pipe will put you into street prepared, though I don't remember if that is DSP or FSP. So you might as well put the throttle body back on;)
Maybe someone could comment on this, I know there's been a flurry of proposals for moving cars in classes, haven't been able to keep track of them all.
For Street touring, you are supposed to run the factory CAT or an functioning replacement that sits in a similar position to the OEM location. I ran street touring last year, and I can tell you there are several honda's that are running with gutted CATs etc. But I am faster, so no reason to really protest.
Parking Lot Hero
2008 WRX daily driver
2003 ZX3 23D Autox Car 42 FSP
"Hella Functional - Raced, Not Hard Parked"