can someone explain this for me? is a streetport legal?

 

You should do a forum search on this to get a full explanation, but I'll give you the general idea.

As far as legality, government people won't even know what the heck you're talking about. So, I don't think there are any laws pertaining to streetporting. Besides, all it does is give you the potential for more hp by feeding more air/fuel through the ports of your engine. Until this mod becomes a hazard to society, there will be no laws concerning it.

Streetporting consists of increasing the size of your intake and exhaust ports (equivalent of boring-out cylinders) that go into and out of your engine. I'm not an expert, so there may be more to it than that. You therefore feed your engine with greater amounts of fuel and air. I.e. you need to upgrade your fuel system in order for your engine to run smoothly (bigger fuel pump/injectors, new ECU to map the air/fuel ratio). This will give you the opportunity to get more power out of your engine because you're feeding it with more air/fuel. Same concept behind getting an aftermarket intake (feeding your car with more air increases power).