I delete what is considered "extra" or "bullshit" (because it is) on things like my 1988 Chevy K5 Blazer (5.7 EFI V8... awaiting a 6.6 EFI V8) or my 1991 Mustang GT (5.0 EFI V8).
What I mean by this is, well let's start with the basics. the Smog pump. This thing literally pumps air at a low pressure into the exhaust, so that it ... smells better? And to make matters worse, there is a wire going to it to make the engine control module (ECM) work. Thankfully it can be jumped out and bypassed.
Next is the catalatyc converter. A Stock older engine needs these to absorb the unburnt fuel and burn it off, so the emissions doesn't "seem" as bad. Yeah those can be deleted and I used to sell the parts to do so.
These cause engine drag, airflow restriction, and add unneeded moving parts to the vehicle.
My Blazer actually gets better fuel mileage without the smog pump or a REAL catalatyc converter. (I have a fake one on it so it can pass inspection). It doesn't need one because it actually burns off all of the fuel fed to it. It's a thing called performance. Granted, there are a few other things done to the engine... and when the 6.6 block (and heads) replace that 5.7, the mileage will remain but there will be power gains.
So while I understand the initial "thought process" behind emissions regulations on cars even though it's nothing compared to what factories, power plants, and other countries produce... why are they so astronomically strict? I mean diesels have parts that gasoline cars have now just to um.... make them look like they're making an attempt and in the long run will cost them money.
IMO the EPA needs to stop fucking exhaust pipes and instead start sticking their dicks into throttle bodies... they'll find much more discomfort.