At this stage I'm not sure about this. Your testing has been good so far. It's been a while since I had to trouble shoot a big burger. I think you may benefit from a chat with a Suzuki dealer technician. Most are usually quite happy to chat. Hopefully you'll find the cause.

Oh no Data! I was hoping you’d have my solution!!!

I think the next course of action is to try a replacement ECU.

Problem solved!!
Thanks to help from the US forum, it turns out the connectors for the TPS and STPS were on the wrong way round. Not when you turn on the ignition, the STVA calibrates and then stops!!!
That’s a relief, I was about to buy another ECU!

Phew! Thank goodness. Bad wiring did cross my mind but didn't think the connectors would fit the wrong way round. But this just goes to show how important it is to not rule anything out! Well done for posting about this & solving the problem.