No. A chip or handheld tuner won't make THAT much of a difference; a few REAL RWHP at the most. It may
feel a bit peppier but it's not going to be like 125 shot of the juice or 10 psi from some form of forced induction. If you modify it with the full round of bolt-on equipment,
THEN tune it to all work together you will notice a fair difference. HCI combo will make a real difference but that is a lot of work/expense. Without getting into a long, drawn-out discussion on octane, compression ratio, air/fuel ratio, premium fuel won't make it have more horsepower. You can tune it with a handheld tuner for a premium fuel tune but it really won't make much RWHP difference. The computer controls the timing and if senses knock, it will pull timing until the knock goes away thus negating the benefits of advancing the timing and using a premium/higher octane fuel.
@Patientzero is correct with a gear change. If you don't mind the extra RPM @ cruising/freeway speed, a set of 3:73's will help it out in the "peppy" department. It won't add any HP but it will take less of what you have to get it going. IMO, 4:10's are a bit too much for a driver unless you have a TALL 6th gear OD. I know people who put 4:10's in New Edge ('99-'04) Mustangs with the automatic transmissions and had shifting troubles until the tuned it to play well with the new gearing. If you go with a gear change, unless you do that kind of work everyday, hire a professional to do it or plan on chasing a whine, grind, or all types of other aggravations as there is an art as well as a science to properly setting up a rear end gear. Also, your speedometer will be off so plan to rectify that. This is for your daughter, correct? IMO, leave it stock down to the air pressure in the tires, LOL! In the long run, life will be soooo much better for you
AND her if you do especially if you're footing the bill. If she insists (Believe me; I know the power of the pouty lip and big, blue, puppy-dog eyes crying"Pleeeeease, Daddy") a handheld tuner will improve the shift points of the transmission and firm up the shifting, add a little throttle response, and make it feel a little more "peppy" without breaking the bank or sending you down the rabbit hole of chasing bolt-on performance from which there is no return. If this is like a father/daughter project and you really want to wake the little 4.6 up, buy a forced induction "kit" from any reputable manufacturer (supercharging is probably easier). They've done the homework, math, testing, etc. and know what to include in a comprehensive package that usually includes the tuner to make it all work well together. Yes, it is more expensive this way but trust me when I say that it's a WHOLE lot better than buying parts to do this kind of thing, one-by-one, then finding out that you missed one or this doesn't work with that and having to take it all apart (AGAIN) to try and fix it. Ask me how I know, LOL! Just my opinion and I'm sure others will vary.
