The reason we have CATs at all is to limit the SMOG that burning petroleum based fuel causes. the catalytic converter is a platinum based honeycomb that bonds to un-burned fuel and burns them in the heat of the exhaust path. a CAT-less downpipe simply removes that honeycomb thereby allowing exhaust gasses to move more freely to the CAT-back system. the lower overall air resistance of a CAT-less system means that the engine does not need to work as hard to exhale exhaust gasses. The HP gains are usually minimal but they ABSOLUTELY require a tune. A decrease in exhaust resistance can cause the turbo to spool faster than expected, / Over simplified/ when the turbo spools faster it crease more boost which in turn leads to more exhaust gasses to push the turbo faster and faster, they call this condition boost creep (when your turbo is spinning overly fast and increasing boost respectively) Boost creep can be controlled with a good tune and with properly setup boost controllers, BPV and BOV.
Im not sure what the regulations are like on Ohio but here in Cali they are sticklers for emissions standard. In Cali we have a visual inspection where the ref will look under the hood for hexaust modifications and then they use a device to find exhaust problems. it would be very hard to pass the sniffer test without the OEM number of cats in CA.
I might also look into a divorced DP, they allow for less turbulence than the OEM but they still pass the gasses through a CAT giving decent sniffer numbers.
TLDR; Cats are there to fight smog, It may/may-not be kosher in Ohio, Look at CATed divorced DP for the best of both worlds. IMHO
13 WRX Hatch