What setting??
 

Should I use the 87 Perf. or the 87 Tow? Will be on interstate 300 mi with 1000 lbs in bed. The interstate has some large long grades (I-64 through WV.)
I get much better mileage with 87 pref. but tow seems easier on the hills.

What are your opinions?

Dave

You can use either tune. The limit for the performance tunes are usually around 2500#s so you could still use it. You might get slightly better mileage with the tow tune though.