The two highest octanes to switch to on my tuner are 91 and 93 i didn't see an 89 which is the middle octane level here in Virginia would i be ok with a 91 tune running on 89, i switched the other day the stang has been running well... i should really buy my own tune instead of just tuning the intake in and upping the octane but i don't know how much or what to pay for...

 

It's definitely not recommended running 89 gas with a 91 tune. Pinging and possible engine damage can result.
If you want to use 89 gas, then you have 2 options:
1- Pull some timing on the 91 tune.
2- Order an 89 tune from BamaChips or Brenspeed.

 

When you ordered your tunes, you could have asked for 89 in lieu of the 91. I have the same octanes available here; 87, 89 and 93.

Do NOT run your 91 tune on 89 octane. If you are, keep adding 93 AND drive easy until you're sure you're up to 91 or higher.

FYI, the 87 custom tune still kicks azz over the stock 87 tune and there's not a heck of a lot of diff between the custom 87 and 89.

 

maybe i ordered the tuner and intake too soon, but how do i order a custom tune i don't think there are any stored tunes on my tuner i just bought a tuner/intake package, how must does a custom tune cost and is it worth it, from what I've heard you shouldn't really mess around with the settings on the tuner unless you really know what your doing so the only things i've done are change the octane and make it so the car recognizes the intake... is there anything else i can safely adjust without blowing my car up?

 

The tuner normally comes with "canned" tunes, which are ok, but there are better ones.
If you don't want to mess with the timing, then add 93 octane to the 89 already in the tank, and drive conservatively as suggested by Nuke. Then, use 91 gas on the next fill up with the 91 tune, and you'll be ok.
The most popular custom tuners are BamaChips and Brenspeed. BC charges $50 per tune, and I believe BS is around the same. They are definitely worth the extra $ versus a "canned" tune.

 

A custom tune will offer higher horsepower, higher lower low-end torque, and almost instant throttle response when compaired to a canned tune. You can get custom Brenspeed tune(s), for any octane level, e-mailed to you which can then be downloaded to your tuner and then to your car. Most of our customers have even reported improved MPG. You will probably see the same as long as you can stay out of the throttle.
Link to our tuning page if you are interested
http://www.brenspeed.com/05-08-musta...ail-tunes.html
Hope this helps