my truck just turned 50k not long ago, I have been running a 40 hp BD box under the hood and the truck ran better with it, but it seems now the truck has gotten better. I dont seem to notice much off the line, but once your rolling say 30 -40 ft, it will just come on and run through the gears nice. the air temps have been about 50 to 65 degrees lately , so that probably has some to do with it, but just naturally does anyone else feel more power with more miles?

Likely getting it broke in now.
Have you worked the engine hard and long lately? Seems to help clean them out, and seat the rings, power is better then.

x2 broken in now. mine started smoking slightly and increased power at almost 40k, also same thing he said mine broke in while i towed my trailer to yellowstone from washington.