New York
Exhaust Systems
New York Consolidated Laws, Chapter 71 (Vehicle & Traf- fic), 375, states that: "Every motor vehicle, operated or driven upon the highways of the state, shall at all times be equipped with an adequate muf- fler and exhaust system in constant operation and properly maintained to prevent any excessive or unusual noise and no such muffler or exhaust system shall be equipped with a cut-out, bypass, or similar device. No person shall modify the muffler or exhaust system of a motor vehicle in a manner which will amplify or increase the noise emitted by the motor or exhaust system of such vehicle above that emitted by the muffler or exhaust system originally installed on the vehicle and such original muffler and exhaust system shall comply with all the requirements of this section." These run-on sentences are all fairly self-explanatory, and pretty restrictive at that.
Nitrous Systems
New York Consolidated Laws, Chapter 45 (Public Health), 3380, provides that "[n]o person shall use nitrous oxide for purposes of causing intoxication, inebriation, excitement, stupefaction or the dulling of the brain or nervous system of himself or another." Further, "[n]o person shall sell any canister or other container of nitrous oxide unless granted an exemption pursuant to this subdivision. n no event shall any canisteror other container of nitrous oxide be sold to a person under the age of twenty-one years." We weren't able to find anything on point regarding use of nitrous oxide systems, so besides checking into the existence of nitrous permits, here again you should assume your bottle must be disconnected or removed while on the street.
OhioExhaust Systems
Ohio Revised Code 4513.22 states: "Every motor vehicle ... with an internal combustion engine shall at all times be equipped with a muffler which is in good working order and in constant operation to prevent excessive or unusual noise, and no person shall use a muffler cutout, by-pass, or similar device upon a motor vehicle on a highway."
Similarly, Ohio Administrative Code 4501:2-1-14 states, "[n]o motor vehicle ... shall be equipped with an exhaust system which would produce any excessive, and/or unusual noise." Also, "[e]very motor vehicle shall at all times be equipped with a standard muffler for said type of vehicle or one that meets all of the above requirements." The requirements are that stated and essentially those of 4513.22, Ohio Revised Code.
Finally, Ohio Revised Code 4513.221 provides that "[t]he board of county commissioners of any county, and the board of township trustees of any township subject to section 505.17 of the Revised Code, may regulate passenger car and motorcycle noise on streets and highways under their jurisdiction. Such regulations shall include maximum permissible noise limits measured in decibels, subject to the requirements of this section." Decibel limits are then set out that involve total noise of the car while in motion, not just exhaust noise. Fortunately, the law includes reference to SAE practices, though not the SAE J1169 set out in the SEMA model legislation (presumably because it doesn't involve cars in motion). So though it seems that this section grants a lot of authority to localities to restrict vehicular noise on their roadways, there is a bit of salvation in that it also states: "No regulation ... shall be effective until signs giving notice of the regulation are posted upon or at the entrance to the highway or part thereof affected, as may be most appropriate."
Nitrous Systems
Ohio Revised Code 2925.31-42 relates to harmful intoxicants and their controlled distribution, and nitrous oxide is classified as such. Most of the wording regarding nitrous has to do with cartridges of it only being approved for use in a food preparation setting, though it may be important for our purposes that it states they cannot be distributed to anyone under 21 years of age. One could presume this also means nitrous can't be distributed in any form (including bottled) to persons under 21.