Standard or Custom Tune

[SeaRay45db]

I have a 2000 GMC Yukon XL with K&N Cold Air Intake and the 24x9 (Largest they make) MagnaFlow. I took the Diablo Tune off before they put the Magna Flow on, was really impressed on how much it made a difference.

Have a long Griswold vacation next week, not towing, standard tune fine or do these mods allow me more flexibility to go to custom tune?

For milage, is it hit or miss with the tune or because of age, anyone have a good idea which one would work the best?

Thanks!

[mikel]

tune for the octane, mileage gains are heavily dependent on driving style.

Thanks

[techntrek]

After a lot of testing between mpg, 87 and Diablo tunes, my best one for economy was the 87 tune.