Octane question
 

I got a 89 performance tune since I always fill up with mid grade in Austin. But I'm in Wyoming for the summer and all the stations in the town I'm in have low grade 85, mid grade 87, and diesel. Sooo, I was wondering if just using the 87 mid grade would be fine over the next 2ish months until I'm back in Texas? Was thinking it would be ok as long as I'm not hard on it and also with the elevation, things wouldn't ignite the same way?

Also, over the next couple of months I'm planing on doing some upgrades: long tube headers w/ resonators (ie cat delete), true duals, underdrive pulleys, and e-fans. Would any of these require me to get a completely new custom tune or would I be able to just adjust some settings myself like the idle RPM and my existing tune woulds still do?

You should be able to run the 87 tune but if you start having engine trouble from it then pull a degree of timing in the custom options menu.

For the mods like the LT headers, cat delete and true duals you'll need your tunes adjusted. The E fans and UD pulleys, however, do not require a rewrite.