Hi everyone, I've had my 2001 550 for a little over 2 months, and it has been an incredible dream come true. I've put 5000 miles on the car so far, and admittedly some of them have been "very spirited". However, today it went into limp mode on the highway, and now it takes a few tries to start. Here are the details: RPMs drop to zero, but the speedometer continues to work. The engine is operating, but there is no tach signal) ASR error light (amber) The exhaust sound changes, as if less than 12 cylinders are working correctly Now a few hours later, I get the "Slow Down" warning after attempting to start (did the limp mode possibly dump fuel into my cats?) When the car does act normally, it happens at random, and then the Check Engine light will come on. Sometimes it will flicker back and forth very quickly, which almost makes me think there is an electrical issue causing this. I thought I could hear a relay clicking, but it could have been my ears. If it was a relay, which one could it possibly be? Additional details: I recently replaced all relays in the fuse box after the wiper/signals/HVAC relay failed (all of them looked very old, and some showing bluing on the contacts). The battery has a full charge and shows 12.5v I let the ECU reset after a couple hours today, but the issue still persists. On two separate occasions the car has been difficult to start, but I thought it was due to bad gas, and a bottle of HEET seemed to fix things. But now I am wondering if those were signs of a deeper issue. I'd love to hear your thoughts. I plan to take it to my independent mechanic this week, but I'm also anxious to connect any dots I may have missed. Thank you!