Audi 90 running on few cylinders

[Definitely Bill Lockwood]

My roommates 88 Audi 90 Q started to run on just a couple of cylinders the
other night.  Until you push the gas pedal all the way down, then the car
will run with all cyl, full power.

So car idles on one or two cyl, but runs at full throttle.

Any suggestions???

BTW it was raining when it happened.

Thanks,
Bill