Well I'm not actually done diagnosing this problem but this is what has happend so far. Gauge reads 1/8 of a tank. Engine idles but bogs and stalls when I punch it. Removed gas cap and there was tremenous suction of air. Refueled, put heat and techron in there and it ran fine until it got to 1/8 again, same problem. Put gas in, and it runs again. This sounds like I ran out of gas but my suburban has a 37 gallon tank and It took only 35 to fill it. My guage has worked fine until now. Could there be a venting problem leading to much vacum in the tank thus causing problems for the fuel pump? Where should I begin to diagnose the fuel gauge? Any other suggestions? A friend of mine had the same problem with his blazer and never figured it out. I have a 1990 350 tbi. Thanks.