Silverado 5.3 liter stalled

I have a 2000 Silverado 5.3 liter, I was driving down the road today 55 miles an hour, the truck just died. I pulled over and tried to crank it. It would barely idle and I pulled off the fuel filter and it had no resistance. It cranked up and it would idle fine, but it would not accelerate. I put it in gear and drove bout ten miles an hour until I got it back to the shop. But it would still not accelerate at all. the highest it would rev to was 1200 rpm.