Get retuned with the cutout open. If you're using an OBD1 ECU, there are easy ways to use a map switch so that you can have a completely different tune with the flip of a switch. That's not necessarily something that you want to do on the fly though, unless the programs are absolutely identical except for the map values. Basically you use a chip that is twice as large as normal, with two complete programs in it. Then you toggle one of the address lines, and you read out of the first half of the chip memory instead of the second half, etc.