It's important to note that the hp gains from modifying the intake are in the upper rpm range when the stock box just chokes. Most modest riding doesn't get into the range that will benefit. To "feel" it is more like noticing the engine not flattening out prematurely.
OTOH, the O2 Mod does affect the lower range (0-20% throttle), but only after the bike warms up and starts using O2 sensor input. Things like hesitation, stalling on takeoff, certain pops, inappropriate chugging and what not related to running a bright blue flame are mostly mitigated.
2013 V Star 1300 Deluxe
OEM Tall Sissy Bar
Memphis Shades Fork Deflectors
Bridgestone Exedra Max Belted Tires
Baron's RSTD 7308 bar