Is a reflash needed after a motor swap?
 

Purchased a truck that had a "new" rebuilt motor installed. It has a little rough idle and a few other things that dont seem just right. I have went through all the normal tune up solutions/checks but not really correcting the symptoms. I asked the previous owner if the PCM was reflashed after the install and he said no. Should it have been reflashed after the new motor? Will/could this help my truck run better?

If it was a stock drop in without any upgrades I don't see a reason to need a reflash.

I was reading on the forums that the reflash could address the throttle issue, which I may have, fuel economy - Im getting around 10, and just replaced the MAF. I disconnected the neg lead for an hour but nothing seemed different. I figured my last option was the reflash

This video is from Makuloco.

Just removing the ground doesn't clear everything. The pcm has a memory that will hold certain codes is how I understand it.
After I installed a new motor my thottle body kept cycling over and over. This fixed it and a few other things. Real easy to do, just have make up a jumper wire. Then your pcm will have to relearn. He explains it very well in the video.

Guess I just need more info about reflash. From what I read, it addresses some issues, but will also set your computer back to stock. Others have mentioned adaptive learning. I feel that my truck was ran for a long period of time with a bad MAF and now runs rich. I installed new MAF and thought that the reflash would correct the fuel air ratio problem I think I have.

Am I wrong?

A reflash is completely clearing the ECU and loading new firmware. While it will, in broad terms, accomplish what you want, you're killing a mouse with a sledgehammer.

Adaptive learning doesn't change the base parameters in the firmware. It makes changes in operating parameters in terms of adjustments from the base parameters. You need to clear the l;earned parameters, which is what the vid above addresses.

Makes sense.

follow up question - am I correct in my way of thinking about adaptive learning? If the truck runs for a long period of time with an issue, the truck will "compensate" or learn to run like that?

Depends on the issue. If it's out of the parameters far enough to throw a code, it kicks into closed loop and runs on the fixed firmware tables without sensor input.