A couple of things that are simple and cheap.

Air filter - I once had a Mini in the 60s that was not running well so I had it tuned by a specialist - on the way home, it died on the highwy. My uncle sent over a real mechanic - he removed the air filter and it ran fine!

Try removing the air filter for a short ride

Mass air plug - once our ’88 745 would not accelerate - I tried it several times on my street - for some reason, I backed up - It ran like a jack rabbit in reverse. I checked the plug on the air sensor, and found that one pin had been pushed back, when I fixed it, it ran fine.

Check th pins on the sensor - this is one plug that is disconnected and reconnected during service. I pulled the boot on the plug and made a line across the wires so I could see if a pin was pushed back.

When I had issues with a 740 that was idle when I tried to sell it - my service writer gave me a small tube of dielectric grease and told me to unplug connections in the engine compartment, clean the connection, apply dielectric grease and zip tie any plugs that I could - this fixed the issues - I did one each week so that if I had a problem, I knew which plug it was.

Good luck, you have plenty of things to try!