fuel lines

I recently replaced the fuel pump in my 96 lumina and it just started running like crap ( missing) the mechanic took it apart and said the lines and injectors were full of some black gooey stuff. Maybe the lines are breaking down. there are 150,000 plus miles on it and I was wondering if anyone else ever heard of this problem
Thanks

I'm almost afraid to ask, but have you done anything to really annoy anyone lately? I've seen a light brown/orange gum in fuel lines from fuel additive buildup liberated once a system is exposed to alcohol from blended fuels, but not black. If it's truly black, and not very dark brown, I'm not sure what it might be. If it's brown, it may be the result of an old (beyond service life) fuel filter finally lettign go and slugging the system with junk. Again, that's usually brown or dark rust colored, not black.

Either way, it sounds like it's time to flush the lines and fuel rails, replace the regulator, replace the filter, and at the very least clean the injectors and replace the injector inlet screens. If you're lucky, the pump may still be intact.