thanks for ur replie but the 50 series is loud isnt it? and also what will it do i thought you must change the whole cat back to make a differance?

The flowmaster 50 and high flow cat goes well with the 4.7, I know it sounds time consuming but your better off just trying the re-starts for now and then if that doesn't work try the stang injectors. I'd go with the upgraded exhaust before switching though that could be all the difference you need, and whoever told you your going to lose power going bigger should give their head a shake.

First off are you getting enough air (aftermarket intake), are you running the stock exhaust (to small), lower temp thermostat?, start at 180* and if it starts to go away try a 160*. Last but not least when you flash it you have to do between 30-40 restarts (this includes driving) before the PCM will actually re-learn the new power curve. So you'll have to re-start at 1* off, do the re-starts, then 2* etc. untill it stops.