Hello all, so I’ve been working on my brothers 2007 Audi A4 S line 2.0t. Originally the car was in limp mode solved that issue turned out to be a gas pedal sensor (accelerator sensor). Now is few days later it had an issue where you’d go to start the car it would start then immediately die. Now I’ve done some research and it’s pointing towards an Immobilizer, however there is no light on the dash for the Immobilizer/anti theft. Anyway it gets towed back and I check for codes etc it has radio codes no communication or static communication. I don’t know if that could be causing the issue, anyway under Immobilizer it had a bunch of codes like glass break hood alarm etc. So I reset them all, and the car started and ran. But the gauges were acting up like the tachometer wasn’t working etc. So my brother then tells me he replaced the headlight switch with a cheap one like 12 dollars from amazon. So we put the factory one in there which worked fine, and the car started no codes other then the radio ones, no issues no limp
mode etc. Now today it’s doing the same thing starts and immediately stalls. I’ve honestly run out of ideas, and my head hurts haha. I’m use to working on American cars not German ones I know they are a whole different animal. Are there any suggestions advice etc. My brother is buying a Immobilizer tonight to have it Incase. Also FYI the car has a APR tune on it don’t know if that matters. Thanks!

Anyone? Could really use some advice here.