Just out on a road trip; did 1,100M yesterday. I left the gas cap by a pump and drove 300 M without any error code. I then bought a new gas cap at an AutoZone. About 150M later at a steady 100 mph the car suddenly lost power and threw error code P1508. It idled rough by the highway. Thinking that the only thing that had changed was the gas cap I pulled the gas cap off and stopped, re-started the car, and cleared the error code. The car then ran fine.
Can there be a connection between P1508 and a gas cap that does not allow the tank to vent as intended, or do I have to look for something else? I run about 1.4 bars on boost, but had not used the power much on the trip.

 

Try this simple adaptation test....

 

I've driven the car another 200M since the P1508 came up and was reset. No more codes. Per your recommendation above I hooked up the Durametric. The only code I found was in the ABS/PSM 5.7 module which gives Current Fault Code 4440 Steering angle sensor. No engine codes. Does this teach us anything?
I am getting a spare Hitachi MAF to carry onboard just in case.

 

None of those faults are related. It can be a glitch. Just drive it and enjoy!!!!

 

So did a search on P1508, which I had yesterday, and thought I would ask for opinions: (my first CEL!)

Did the Cars and Coffee, went for an 80 mile spin, which included some "fun". Driving more "normal" on freeway home, engine went to idle(while doing 75mph) and CEL came up with Check Engine Light.

Car didn't seem to go into a limp mode, would just idle? Coasted to side, of busy freeway, then 1/4m to off ramp, and 1/4 mile later into parking lot, all at idle.

Shut car off, checked engine bay, checked underneath, no issues I could see.

Started car, car now revs in neutral. In gear, CEL is there, but car seems to reverse and drive normal. All normal sounds.

Drove home, low speed, no issues?

Stuck in OBD reader, fired up phone, P1508 Code. Did the research, cleared the code, looked everything over again.

Took for a 50 mile drive, no issues, next day.

Car has 66K, tip, stock, I have put on 3K, no issues, till this. Don't know much about previous history.

Should I wait or preemptively do something?

 

As I started the thread I'll add my two cents worth: While I have plenty of experience with error codes P1508 has only showed up the one time. This happened under the circumstances listed at the top. The only thing I know that changed before or after is having an aftermarket gas cap at the time.
Scary when it happened, though, as I thought I was to call AAA next, but it ran just fine after re-start and P1508 has not come back.

Good luck!