Newly installed custom tunes

[Paw Paw]

I got my custom tunes on 6/14/2010 and installed them as soon as I got home that day . Just minutes after installing my tunes , I got bad news that my sister had passed away . Things for me have been pretty hectic since then.
I am running it in 87 performance tune .
The first thing I noticed was the better throttle responce and shifting and an increase in gas mileage . Been doing a lot of driving back and forth to the mountains of Va. from the Triad in NC.
Just took a trip today and noticed that my mileage had fell back down and that performance was sluggish.
While driving real slow through a parking lot the trans. seemed to be in neutral position - like it was between gears. Feed it some fuel and it would go back in gear and go . Let off and it seemed like it was coasting again.
Anyone have any idea what may be going on ?
Thanks in advance
PAW PAW