I think that's a subjective question. 500 on what dyno? Dynojet? Mustang dyno? Virtual dyno? I think on a dynojet or virtual dyno 500 on a stock motor isn't asking too much. For my car to do it on the mustang dyno and expect any kind of longevity would be asking for a bit much I think. I'm pretty partial to the fp red as a stock frame upgrade. FP makes damn good turbosOn a stock engine? Maybe 480-500, but you don't wanna push it.
On a built engine I've seen them hit 550.