re - not allowing tinkering, etc.
A lot of the no-tinkering is built into the regulations for the same reason that speed limit signs don't change based on traffic density; and stop signs & lights don't vanish at 3 am. It is easier to set a "one size fits all" than to enact (and enforce) highly flexible regulatory schemes. An individual is very very unlikely to come up with a better emissions system than a new car will have.
The laws are designed to deal with the millions of Joe Averages out there -- if there are any exceptions, they are going to be aimed at poor people (or people with good lobbyists... oddly enough they are not poor).
BTW< Porsche has always prided itself on its excellence in engineering low pollution and high mileage cars. Think about cars with comparable performance -- which ones can match a Porsche for fuel economy or emissions. There is only one such company (hint - it ain't Italian or American). Well, ok two companies...
Because all threads are worthless without pics, here is a nice pic to look at while you think about the company of Mr. Light Weight himself and the other one...
