Almost completed a 2200 mile cross country run when engine stalled on interstate.

Engine acted as if starved of fuel and held idle speed but would not accelerate or even maintain highway speeds. Performance gradually decreased, eventually running down to idle and then stopping.

Performed Diagnostic tests with codes 553 and 311 pointing to problems with the thermactor system. Checked vacuum hoses and replaced secondary air diverter solenoid vale (still signals a code 553). Not sure how these codes would affect highway performance. We will be needing to use this vehicle to make a return drive in a few weeks and don't want to spend time on the side of snowy road someplace in Texas.

Fuel filter was replace prior to trip and checked at shop (good flow). Possible contaminated fuel (little vehicle use prior to trip) which might indicate intermittent performance disruption (missing at high speed, usually following rough pavement enounters). At time of shutdown drove across a sustained distance of "bad road" in Los Angeles which might have tossed up the balance of the tank's contamination. Engine starts and runs and I am working up to taking some short test drives to gain confidence for the continued use of this vehicle.

Need to determine if 1)fuel or 2) Thermactor system would cause the engine shutdown.
Thanks,
Steve