+20-25 HP requires some careful tweaking. Several ways to go about it..I suggest
1) 7"-9" K&N filter on BAT adapter with screen ($80)
2) Custom cool air box & ducting (make it yourself)
3) Pro-M 75mm MAF meter ($175)
4) Optimize SVT throttle body and rubber air tube
5) Optimize LIM butterflies (or remove if you are good with custom dyno/laptop tuning of a chip - investigate carefully first)
6) Gut precats (free) or headers - more noise, investigate carefully first)!
7) High flow Y- pipe (get it ceramic coated!) ($250)
8) Upgrade resonator & mufflers or catback if you want to spend more ($200-$550)
9) Ford Racing wires & new plugs if you have ($65) greater than 35K miles along with new fuel filter
9) Last...Dyno tune ($100-150 per hour) with wide band monitoring A/F - custom burn a chip ($250 + custom program $125), EEC tuner ($450) best & soon avail. Apexi-SAFC ($300), Pro-M optimizer ($150) cheapest but least capability.
Above combo gives high probability of 185+ FWHP, about 20 over stock . Speed costs money..
Add Dual mode damper ($135 from THM) for reliability. Keep oil at full mark always, happy motoring!
