How do you make your slow car fast without swapping the engine?

vehicle swap

alternatively, a nitrous kit

>not being a faggot

I'll take that to mean "improve driving skill."

>I can't do this to my Legacy GT because I live in California and I'd have to jump through hoops like a fucking seal to get it re-registered and smogged

ad quite thfuckin gigle m8

Try getting a civic to race alongside things like RX-7s without losing things like air-conditioning to weight reduction and ride comfort to stiffer suspension.