I just added 3 inch full exhaust with 50 series flowmaster mufflers to my 440 950 hp has 78 all the way around and power valves, should I jet it fatter or leaner when you add exhaust? Thanks

Typically you would richen when a restriction has been removed.
However if you don't know whether you were rich,lean,or dead on before I would find out where you are now first before making changes.
Unless you were running 2" pipe or single exhaust before you may not have to change it at all.

The car was running good had 2 inch tti's open headers I was just wondering what other people ran into that had there car running good and then put exhaust on. Did they richen the carb or lean it down. Thanks

I didn't jet either way on my Duster when I went from open headers to a 3.5" exhaust, X-pipe, Dynomax bullets & turn-downs; plugs looked the same, no appreciable change in time slips. 368" SB, 904, 5.38, 13x31s, 3000lbs, low-10s footbrake car, exhaust was added when I was running it @ sea level. Not the same combo as yours, but that was my experience.
Best way to tell on yours is to do a plug-check run.