New Mustang Owner

[Mr 5 0]

Short of bolting on a turbocharger, not a lot, without spending some money and doing serious work on that engine. Start with a total tune up and then consider a steeper rear axle ratio for more low-end performance (and a lot more shifting, if it's a 5-speed).
I'm (obviously) a V-8 guy, but realistically the 2.3 was made for economy, it's in a 3200 pound car and it's not going to respond to small modifications, as a 5.0 does. This is why a lot of folks either give up on the 4-cylinder Mustangs, or end up putting a 5.0 in there. I would do the best you can with what you have and try to be content with that, or consider an engine change or a turbocharger set-up, which is expensive. Nitrous is a quick-fix to the performance problem...but even a small shot will probably destroy the head gasket and only yield 16-second quarter mile et's. The 2.3 simply is what it is. A low-powered, gas-saving engine, meant for mundane duties, not high performance.