Stock ecu reflash software

Where do I get the software to reflash a stock ecu and is there one that is better than the others and are there unlimited licenses or is that something u have to buy ever time u use them

It depends on the vehicle. For most US Domestic manufacturers, you can probably look to HPTuners for a solution. They have both single ECU licenses (I charge the customer to add a licence for his car to my HPTuners interface), and unlimited for a specific model (ie, if your customer base all have the same ECU, you can buy a license to allow you to turn an unlimited number of those). Look under the Vehicles menu on https://www.hptuners.com/ for a list of what they support.

There are plenty of other tools, but HP Tuners fits most of the hot rods that show up in my shop.

As David mentioned, let us know what vehicles you are hoping to cover. The appropriate tool varies, and then how they handle costs varies as well.