1991 Nissan 300ZX Gas smell

I have a very strong gas smell. I do not have any visable leaks, and have replaced the fuel pump. I also have a problem sometime with when I am in 3rd or 4th grear it will sputter out at like 300rpm and I have to shift to a higher or lower gear for it to stop and it does not always stop. I think that one of my cylinders may be miss firing and jus getting filled with gas. If this is the issue wut else should I look for if its that?