I haven't ran a stock intake since May 2010, a week after I got the truck lol!
And have gone from stock -> K&N drop in-> Airaid-> modified Airaid -> Volant -> modified Volant. Each was better than the previous.
I also have accumulated a lot more supporting mod's, so it wouldnt be fair to say I've gone from a 15.3 quarter mile to 13.8 on intake alone,,,but its certainly a supporting mod that helped me get there.
I went through three different tuners as well, 3 sets of tires and track test the shyte out of every combo I can imagine.
IMHO, Stock sucks no matter what you're comparing to for aftermarket performance
Intake/Throttle Body/Tuning/Muffler/Y-Pipe/Torque Converter/Tires
I imagine if I tossed the old stock box on now I would be very disappointed.