Is this my fuel injection?

2003 chevy 4.3 v6

I was driving down the road and I thought I had ran over something in the road, it made a little thud noise. Then a little while later I noticed my truck wasnt running right. About 10 miles down the road my engine light came on. I took it to the chevy dealer and the code they got was an 0300 which is a misfire. They tested my compression and it was ok and they said they tested my injectors and they didn't balance. I took it home and put a new fuel filter on hoping for the best but it seems to be worse. It still idles bad and makes the thys noise when im up around 30mph. I dont want to have to replace the fuel injection. Also my buddy was driving behind me and said he could smell gas real bad. Waht do you think. Thanks