Use to be a blast to do a complete engine modification, bore and stroke it, roller cams, port the intake manifold, headers for the exhaust, completely different fuel system, when this was legal.
Screwing around with the air intake, exhaust doesn't do a darn thing, and just a waste of money, plus up to a $35,000 fine if emissions are affected, but haven't heard of anyone getting caught.
Today, we have more 500+ HP vehicles than ever before in our history. If you want a faster car, don't know why, can't use it legally on the road, buy one. Saw that Dodge commercial for a 207 mph vehicle.
EPA basis for emissions is based on the make, model, engine, and year, so you still can drop a large Caddy V-8 in a 48 Ford coupe, did that, called it a sleeper back then. But you may get a heart attack when you apply for insurance, a $10,000 liability only policy may cost you $9,999.99 per year. Didn't care back then, but sure do today.
Ha, by the year 2000, we all will be driving 300 mph, try more like 15 mph. 2-3 mph on a busy interstate that never kept up with traffic.