There are a couple factors at play here:
- Different devices in different environments will report different power values.
- Lots of people seem to observe higher power numbers outside than inside.
There’s a bunch of existing discussion. If you can use the Tarmac with the power meter on the Tacx, you could set up Power Match and at least have a consistent power source. If you can’t, use the 243 number indoors, and bump it up when you go outside. TR FTP tests are for calibrating your workouts on the device you’re using to train, so it’s important to use the number the device gives you.
TR doesn’t plan to support multiple FTP profiles.