Internet access doesnt work with LB as gateway and snat disabled but if we use a snatpool it works. Does anybody know why?

I agree with Chris. There's one more thing that could be an issue. Does the FW have an interface on the same network as the server that's trying to get to the internet?

Might be a good idea to give us a look at the config for the FWD as well as an idea of the physical connections involved.