Why does my Ami feel like it's lifting on the banked corners?

That light inside front is the classic Ami thing on a banked oval, and yes, the fix is nearly always at the back. The car rolls a lot because the rear is soft and tall, so on banking all the load piles onto the outer front tyre and the inner one just skims. What the others have almost certainly done is add rear camber shims and often small track spacers at the back, so the rear leans into the corner instead of flopping over. Some also fit firmer rear spring pads. Once the rear stops rolling, the front stays planted and the twitch goes away mostly on its own.

Not sure I buy the camber shim theory. My Ami did exactly the same thing and the shims did nothing, becasue the wheel going light was a tyre pressure problem all along. The event sheet had everyone on one number, but a car that light needs way less air than a normal hatch to keep the contact patch on the banking. Dropped a chunk out of all four and the twitching basically stopped. Worth trying that before you start bolting parts on, since it costs nothing and takes ten minutes at the track.

Same experiance here with the pressures. I run mine a good bit softer than the sheet says, especally at the back, and the hopping on the banking settled right down. One thing to watch though, check them cold between sessions, because after a few laps out there the tyres heat up and the gauge reads way higher than what you set. I kept chasing my tail for two race days before I figured that out. Also on the gearing question, the 45 motor stays in for our spec class, so I'd double check what your series says before buying anything.

I only do the indoor kart-style events with mine, so no banking to worry about, but the rear of the car was all over the place there too until I realised I had a toolbox and spare jumper strapped behind the seat. Moved that stuff forward and it settled a lot. Might be worth checking what you're carrying, especially with the harness pulling you into the seat differently than stock. Also keen to hear what people say about the gearing question, because I'm on the 45 as well and the rulebook lost me around page three. Did anyone actually get pulled up at scrutineering for motor stuff?