I've been following this but holding back because I don't have a Basato, BUT I do have a well-running bandsaw.
It had been fettled when I got it, but I decided on a full strip down and clean, to start on the right note, so to speak. Whilst doing this, I discovered that the two wheels were out of alignment vertically, and that the bottom wheel wasn't set up to track properly. I had to modify the bottom spindle (file flats on the end opposite the wheel) so that I could hold it in the correct position, etc., but once I'd got it right, it ran (and still runs) really well, with almost no discernable drift, even when I go from 5/8" (biggest practical blade it'll tension properly) to 3/16" for a quick job.
Like you, I use Ian's blades and find them brilliant.
Have you checked the geometry fully? I know it's easier on the Basato, because Steve M uses one to illustrate the process on his video - on my SIP you can't just put a straightedge between the wheels as there are two covers, not the single one of the Basato. I had to use offsetting blocks, but it's a doddle on yours.
My guess is that there is something fundamental wrong with the geometry, causing you to compensate for it elsewhere (e.g. in the top wheel tracking), but in reality causing the issue you're seeing. To cause sparks means there is considerable pressure on the back guide, which CANNOT be right. The only things I can think of to cause that on a correctly set up machine would either be very blunt blades or too fast a feed speed, either of which would be obvious to you (and everything would be complaining).
I'd check the geometry thoroughly from first principles. I'm not a betting man, but...
E.
