in the fine state of massachusetts its illegal to modify your exhaust in such a manner strictly to make it louder

states vary by whats legal and what's not

 

i know in Cali, you can't lower you car so that the height of the top of your headlights is lower the 22" or something crazy like that

 

keeping a car too low is foolish because of speed bumps, dips, and other knicks in the road, not legality issues.
running high-octane gas(coming out of a barrel, not a conoco pump) is not for road use, but won't give you much benefit unless your engine is designed for high enough compression to merit high-octane gas. you need to have functional turn signals, head lamps, running lights, brake lights or you can be knicked for that. different localities have different sound rules, so you might not want to opt for the fart can exhaust if your municipality has a strict noise law, or if you have a scrap of sense. If you live in California, I'd suggest moving out because the hippies there are hard at work to make all cars illegal. Best thing to do is consult your police department as to what you can do. They can give you all the specs as far as decibel, inches, and octane and whatever else is kip to do and don't.

 

I just wanna know compltely out of curiousity. Yeah i was wondering more like engine/ECU modifications, but keep on with the body work too, thats interesting to me.

 

Anything that is not DOT approved. Driving with Full Slicks on the street, operating nitrous oxide on the street, things of that nature.

 

Breather, if its the cheap kind u can Fail a smong test...

 

"Smog." My bads lol

 

A breather will not cause you to fail smog tests, that line just connects to the CAI if u dont use a breather filter.