Looking in the latest issue of one of the trade magazines and the ads, it seems that the hot items for gas, are chips (your choice of poison), programmers (already discussed), air intake (K & N, but we know what kind of discussion that causes w/diesels, and others same as w/diesels), headers and/or cat back exhausts, and MASS AIR FLOW SENSORS.
Granatelli seems the hot brand for this, according to the adds, + 10-23HP, 47% more airflow, installs in about 10 minutes, compatible with all electronics and aftermarket performance equipment, WON'T VOID WARRANTY, INDUSTRY LEADING????... .
... and there is always BANKS gas aftermarket add on stuff!
Don't know myself, but this seems to be what is advertised heavily, and each seems to say 10HP and up, SO?