If you kind of read between the lines in regards to the smog testing, I'm thinking that "they" don't want you driving around in a a poorly tuned junker or a race car with open headers. There are millions of cars built between 1976 and the OBDII cars, NONE of them are allowed to have any modifications to perform better?

So, do they start looking at engine block numbers? Like say you put a 360 in place of the 318 in your 1976 D100 they fail you? Or if you put a Performer intake with a Holley carb on said lo-po 318 they say no dice? What if you spend the time and effort to tune it well enough to pass, what then?

With my truck, I am kind of doing what "they" want for my own benefit. I'm getting rid of the 'performance mods' the P.O. did - huge cam, hi-rise intake etc. I drive the thing regularly on longer trips (110 miles+) so fuel economy is somewhat important. I bought a milder cam and a low-rise intake to replace the overkill Ricky racer stuff in hopes of seeing double-digit mileage.

I also got an A/F gauge to monitor how rich the thing was. When you tune your junk correctly I would guess the added benefit is reduced emissions. (to a point) I have no idea how my truck would look on a sniffer test in California but I'm guessing it would fail miserably. I suppose that's the issue...

Regardless, there's really none of that critical thinking involved with a newer truck, it's just replacing stuff that doesn't work if you can't do any 'modifications'. Have fun messing with EVAP and EGR codes.