Car running poorly after sitting for a while?

Since August 2025 I have used my car very little. I occasionally started it up, with the first time being over a month after parking it. It took much longer to start and then ran really rough. I let it warm up and it was not as good as it was back when I was using it regularly.

When I tried to drive it from my backyard it stalled. I started it again and it was very rough and was 'hunting' for power (or whatever it is called) as when I pressed the accelerator it threatened to stall. I finessed the throttle and slowly got it to the point where it could rev without problems.

So I made an effort to start it more often, like every two weeks.

Recently I took the car out and about 2 miles down the road while turning left it nearly stalled mid-way through the turn. I had to press the clutch in and let the car coast around the corner so the engine wouldn't stall. I pulled over and finessed the throttle again and got it to the point where it revved cleanly.

After it was left for a couple of days after this incident a friend took it out and it stalled on him too - approximately the same distance down the road (2 miles or so). He was able to get to where he was going though.

The battery is relatively new being purchased in November 2024 (not 2025). There is a new CDN$500 Bosch alternator installed (though the bottom bolt has still not been sorted out as no-one at BMW knows what size it is and they can't find it anywhere on their system).

I new fuel pump was installed in July of 2025.

So. Any ideas?