Mine worked fine matey, had a gauge on it and kept checking the pressure was as it should beget the fse boost valve off there mate, they are known for upping or lowering the fuel pressure as they are pants, it wouldnt surprise me if its running mega rich.
have you got a gauge on there???? do you know what pressure your running???
once more it may not be fuel and it may just be exhaust and you could be running lean which = melted pistons.
also what engine is it???? any mods to engine????