You might as well do them both at the same time, that way you can knock two birds out with one stone. I have done the downpipe and im fixing to do the uppipe, but i wish i would have went with both at the same time.
Well considering stage 2 isnt anything but exhaust flow and reprogramming id say its pretty safe for street and everyday use. Now when you start upgrading turbo and fuel systems thats another story.